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Question 601Question

Line segments ACAC and BDBD intersect at point EE such that segment ABAB is parallel to segment CDCD. If the length of AEAE is 55, the length of CECE is 1010, the length of BEBE is x2x - 2, and the length of DEDE is x+4x + 4, what is the value of xx?

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Answer: 8

Answer

8
Since segment ABAB is parallel to segment CDCD, the alternate interior angles EAB\angle EAB and ECD\angle ECD are congruent, and vertical angles AEB\angle AEB and CED\angle CED are congruent. By the Angle-Angle (AA) similarity theorem, triangle ABEABE is similar to triangle CDECDE. The ratio of the lengths of corresponding sides is equal, so AECE=BEDE\frac{AE}{CE} = \frac{BE}{DE}. Substituting the given lengths gives 510=x2x+4\frac{5}{10} = \frac{x - 2}{x + 4}. Simplifying the left side to 12\frac{1}{2} and cross-multiplying gives x+4=2(x2)x + 4 = 2(x - 2), which expands to x+4=2x4x + 4 = 2x - 4. Solving for xx yields x=8x = 8.

Step-by-Step Solution

1
Establish the similarity of triangles ABEABE and CDECDE.
ABECDE\triangle ABE \sim \triangle CDE
Since segment ABAB is parallel to segment CDCD, alternate interior angles EAB\angle EAB and ECD\angle ECD are congruent, and vertical angles AEB\angle AEB and CED\angle CED are congruent. Thus, the triangles are similar by AA similarity.
2
Set up a proportion using the ratio of corresponding sides.
AECE=BEDE\frac{AE}{CE} = \frac{BE}{DE}
In similar triangles, the ratio of corresponding side lengths is constant.
3
Substitute the given algebraic expressions and segment lengths into the proportion.
510=x2x+4\frac{5}{10} = \frac{x - 2}{x + 4}
The given values are AE=5AE = 5, CE=10CE = 10, BE=x2BE = x - 2, and DE=x+4DE = x + 4.
4
Simplify the fraction and solve the linear equation for xx.
x=8x = 8
Simplifying 510\frac{5}{10} yields 12\frac{1}{2}. Cross-multiplying gives 1(x+4)=2(x2)1 \cdot (x + 4) = 2 \cdot (x - 2), which simplifies to x+4=2x4x + 4 = 2x - 4. Subtracting xx from both sides and adding 44 to both sides gives x=8x = 8.

Key Concept

Triangle similarity criteria (specifically AA similarity) and using proportions of corresponding sides in similar triangles to solve for unknown variables.
Question 602Question

In triangle ABCABC, the side lengths are AB=AC=5AB = AC = 5 and BC=6BC = 6. Point DD is the midpoint of side BCBC, and point EE lies on side ABAB such that segment DEDE is perpendicular to side ABAB. What is the length of segment DEDE?

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Answer: 2.4

Answer

The length of segment DEDE is 2.42.4 (or the equivalent fraction 12/512/5).
The correct answer is 2.42.4 (or 12/512/5). In the isosceles triangle ABCABC with AB=AC=5AB = AC = 5, the median ADAD to the base BCBC is also an altitude. Since DD is the midpoint of BCBC, we have BD=3BD = 3. Applying the Pythagorean theorem to right triangle ABDABD gives AD=5232=4AD = \sqrt{5^2 - 3^2} = 4. Since DEDE is perpendicular to ABAB, triangle AEDAED is a right triangle that shares angle AA with right triangle ADBADB. Therefore, triangle AEDAED is similar to triangle ADBADB. The ratio of the opposite side to the hypotenuse in both triangles must be equal: DEBD=ADAB\frac{DE}{BD} = \frac{AD}{AB}, which gives DE3=45\frac{DE}{3} = \frac{4}{5}, or DE=2.4DE = 2.4.

Step-by-Step Solution

1
Determine the properties of the altitude ADAD in the isosceles triangle ABCABC.
ADAD is perpendicular to BCBC, and BD=3BD = 3.
In an isosceles triangle, the median to the base is also the altitude to the base. Since DD is the midpoint of BCBC, BD=BC2=62=3BD = \frac{BC}{2} = \frac{6}{2} = 3, and ADB=90\angle ADB = 90^\circ.
2
Calculate the length of segment ADAD using the Pythagorean theorem in right triangle ABDABD.
AD=4AD = 4
Applying the Pythagorean theorem to right triangle ABDABD gives AD2+BD2=AB2AD^2 + BD^2 = AB^2. Substituting the known lengths yields AD2+32=52AD^2 + 3^2 = 5^2, which simplifies to AD2=259=16AD^2 = 25 - 9 = 16, so AD=4AD = 4.
3
Find the length of segment DEDE using triangle similarity.
DE=2.4DE = 2.4
Since segment DEDE is perpendicular to side ABAB, AED=90\angle AED = 90^\circ. The right triangles AEDAED and ADBADB share the angle at AA, so they are similar by AA similarity (AEDADB\triangle AED \sim \triangle ADB). This allows us to set up the ratio of corresponding sides: DEBD=ADAB\frac{DE}{BD} = \frac{AD}{AB}. Substituting the values gives DE3=45\frac{DE}{3} = \frac{4}{5}, which results in DE=125=2.4DE = \frac{12}{5} = 2.4.

Key Concept

Properties of isosceles triangles, the Pythagorean theorem, and right triangle similarity theorems.

Alternative Method

Alternatively, the length of DEDE can be found using the area of right triangle ABDABD. The area of triangle ABDABD is 12×BD×AD=12×3×4=6\frac{1}{2} \times BD \times AD = \frac{1}{2} \times 3 \times 4 = 6. The area can also be expressed using the hypotenuse ABAB as the base and DEDE as the height: Area=12×AB×DE=12×5×DE\text{Area} = \frac{1}{2} \times AB \times DE = \frac{1}{2} \times 5 \times DE. Setting these equal gives 52DE=6\frac{5}{2} DE = 6, which yields DE=2.4DE = 2.4.
Estimated Time:1m 30s
Question 603Question

In triangle ABCABC, point DD lies on side ABAB and point EE lies on side ACAC such that segment DEDE is parallel to segment BCBC. The length of segment ADAD is 2x+12x + 1, the length of segment DBDB is x+1x + 1, the length of segment AEAE is 1010, and the length of segment ECEC is 66. What is the length of segment ABAB?

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Answer: 8

Answer

The length of segment ABAB is 8.
By the Triangle Proportionality Theorem, since segment DEDE is parallel to segment BCBC, the segments on the transversal sides are proportional: ADDB=AEEC\frac{AD}{DB} = \frac{AE}{EC}. Substituting the given expressions and values yields 2x+1x+1=106\frac{2x + 1}{x + 1} = \frac{10}{6}. Simplifying the fraction on the right side to 53\frac{5}{3} and cross-multiplying gives 3(2x+1)=5(x+1)3(2x + 1) = 5(x + 1). Solving this equation yields x=2x = 2. The length of segment ABAB is the sum of ADAD and DBDB, which is (2x+1)+(x+1)=3x+2(2x + 1) + (x + 1) = 3x + 2. Substituting x=2x = 2 gives AB=8AB = 8.

Step-by-Step Solution

1
Set up the proportion using the Triangle Proportionality Theorem.
ADDB=AEEC\frac{AD}{DB} = \frac{AE}{EC}
Since segment DEDE is parallel to segment BCBC, it divides the sides of triangle ABCABC proportionally.
2
Substitute the given values and simplify the constant ratio.
2x+1x+1=53\frac{2x + 1}{x + 1} = \frac{5}{3}
The length of segment AEAE is 10 and ECEC is 6, so AEEC=106=53\frac{AE}{EC} = \frac{10}{6} = \frac{5}{3}.
3
Cross-multiply and solve the linear equation for xx.
x=2x = 2
Cross-multiplying gives 3(2x+1)=5(x+1)3(2x + 1) = 5(x + 1), which simplifies to 6x+3=5x+56x + 3 = 5x + 5. Subtracting 5x5x and 3 from both sides yields x=2x = 2.
4
Calculate the total length of segment ABAB.
AB=8AB = 8
The total length ABAB is the sum of ADAD and DBDB. Thus, AB=(2x+1)+(x+1)=3x+2AB = (2x + 1) + (x + 1) = 3x + 2. Substituting x=2x = 2 gives 3(2)+2=83(2) + 2 = 8.

Key Concept

Triangle Proportionality Theorem and Similar Triangles

Alternative Method

Instead of using the Triangle Proportionality Theorem directly, we can use the similarity of triangles ADEADE and ABCABC. Since DEBCDE \parallel BC, we have ADEABC\triangle ADE \sim \triangle ABC by AA similarity. This gives the ratio of corresponding side lengths: ADAB=AEAC\frac{AD}{AB} = \frac{AE}{AC}. Substituting the expressions yields 2x+13x+2=1016=58\frac{2x + 1}{3x + 2} = \frac{10}{16} = \frac{5}{8}. Cross-multiplying gives 8(2x+1)=5(3x+2)    16x+8=15x+10    x=28(2x + 1) = 5(3x + 2) \implies 16x + 8 = 15x + 10 \implies x = 2. Then, AB=3x+2=3(2)+2=8AB = 3x + 2 = 3(2) + 2 = 8.
Estimated Time:1m 30s
Question 604Question

Points AA, BB, and CC lie on a circle with center OO. The length of the minor arc ACAC is 49\frac{4}{9} of the circumference of the circle. What is the measure, in degrees, of the inscribed angle ABC\angle ABC?

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Answer: 80

Answer

The measure of the inscribed angle is 80 degrees.
The correct answer is 80. The minor arc ACAC constitutes 49\frac{4}{9} of the circle's circumference, which corresponds to an arc measure of 49×360=160\frac{4}{9} \times 360^\circ = 160^\circ. By the Inscribed Angle Theorem, the measure of the inscribed angle ABC\angle ABC is half the measure of the intercepted arc, which is 12×160=80\frac{1}{2} \times 160^\circ = 80^\circ.

Step-by-Step Solution

1
Determine the degree measure of the minor arc ACAC.
The measure of minor arc ACAC is 160160^\circ.
Since a full circle has a circumference corresponding to 360360^\circ, minor arc ACAC has a degree measure of 49×360=160\frac{4}{9} \times 360^\circ = 160^\circ.
2
Calculate the measure of the inscribed angle ABC\angle ABC.
The measure of ABC\angle ABC is 8080^\circ.
According to the Inscribed Angle Theorem, the measure of an inscribed angle is half the measure of the arc it intercepts. Thus, the measure of ABC\angle ABC is 12×160=80\frac{1}{2} \times 160^\circ = 80^\circ.

Key Concept

Inscribed Angle Theorem and Arc Measure
Question 605Question

In the xyxy-plane, the graph of the equation x2+y210x24y+69=0x^2 + y^2 - 10x - 24y + 69 = 0 is a circle. What is the distance between the center of this circle and the origin?

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Answer: 13

Answer

The distance between the center of the circle and the origin is 13.
Completing the square on the given equation yields standard form (x5)2+(y12)2=100(x - 5)^2 + (y - 12)^2 = 100, identifying the center of the circle as (5,12)(5, 12). The distance from (5,12)(5, 12) to (0,0)(0,0) is calculated using the distance formula: 52+122=169=13\sqrt{5^2 + 12^2} = \sqrt{169} = 13.

Step-by-Step Solution

1
Group the xx and yy terms and complete the square for each variable.
(x5)2+(y12)2=100(x - 5)^2 + (y - 12)^2 = 100
By rewriting x210xx^2 - 10x as (x5)225(x - 5)^2 - 25 and y224yy^2 - 24y as (y12)2144(y - 12)^2 - 144, the equation becomes (x5)225+(y12)2144+69=0(x - 5)^2 - 25 + (y - 12)^2 - 144 + 69 = 0. Combining the constant terms gives (x5)2+(y12)2100=0(x - 5)^2 + (y - 12)^2 - 100 = 0, which simplifies to standard form.
2
Identify the center of the circle from the standard form (xh)2+(yk)2=r2(x - h)^2 + (y - k)^2 = r^2.
The center is (5,12)(5, 12).
Comparing (x5)2+(y12)2=100(x - 5)^2 + (y - 12)^2 = 100 to the standard form shows that h=5h = 5 and k=12k = 12.
3
Use the distance formula to calculate the distance between the center (5,12)(5, 12) and the origin (0,0)(0, 0).
13
The distance formula is d=(x2x1)2+(y2y1)2d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}. Substituting the points gives d=(50)2+(120)2=25+144=169=13d = \sqrt{(5 - 0)^2 + (12 - 0)^2} = \sqrt{25 + 144} = \sqrt{169} = 13.

Key Concept

Equations of Circles in the Coordinate Plane
Question 606Question

A rectangular field has a diagonal path of length 4040 meters. The length of the field is 88 meters greater than its width. What is the width, in meters, of the field?

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Answer: 24

Answer

The correct answer is 24.
Letting ww represent the width of the rectangular field in meters, the length is w+8w + 8 meters. The diagonal forms the hypotenuse of a right triangle with the width and the length as legs. By the Pythagorean theorem, w2+(w+8)2=402w^2 + (w+8)^2 = 40^2. Expanding this yields 2w2+16w+64=16002w^2 + 16w + 64 = 1600, which simplifies to w2+8w768=0w^2 + 8w - 768 = 0. Factoring this equation gives (w24)(w+32)=0(w-24)(w+32) = 0. Since width must be positive, the width is 24.

Step-by-Step Solution

1
Represent the dimensions of the rectangular field.
Let the width of the field be ww meters, so the length is w+8w + 8 meters.
The problem states the length is 8 meters greater than the width.
2
Apply the Pythagorean theorem.
w2+(w+8)2=402w^2 + (w + 8)^2 = 40^2
The diagonal of a rectangle forms a right triangle with the width and length as its legs.
3
Simplify the quadratic equation.
w2+8w768=0w^2 + 8w - 768 = 0
Expanding the equation gives 2w2+16w1536=02w^2 + 16w - 1536 = 0, which simplifies when divided by 2.
4
Solve for the variable ww.
(w24)(w+32)=0(w - 24)(w + 32) = 0, so w=24w = 24 or w=32w = -32.
Factoring the quadratic equation gives the possible values for the width.
5
Determine the valid physical width.
w=24w = 24
Since the width of a field must be positive, we reject the negative solution.

Key Concept

Using the Pythagorean theorem to relate the sides of a right triangle in a geometric word problem.
Question 607Question

In the xyxy-plane, a circle with center at the origin passes through the point (0,8)(0, 8). A line tangent to the circle at point TT passes through the point P(15,8)P(15, 8). What is the length of segment PTPT?

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Answer: 15

Answer

The length of segment PTPT is 1515.
The radius of the circle is 88 because the circle is centered at (0,0)(0,0) and passes through (0,8)(0,8). The distance from the center O(0,0)O(0,0) to point P(15,8)P(15,8) is OP=152+82=17OP = \sqrt{15^2 + 8^2} = 17. The radius OTOT is perpendicular to the tangent segment PTPT at point TT, forming a right triangle OTP\triangle OTP with hypotenuse OPOP and legs OTOT and PTPT. Using the Pythagorean theorem, PT=17282=15PT = \sqrt{17^2 - 8^2} = 15.

Step-by-Step Solution

1
Determine the radius of the circle
Radius r=8r = 8
The circle is centered at the origin (0,0)(0, 0) and passes through (0,8)(0, 8), so the distance from the center to this point is the radius.
2
Calculate the distance from the origin O(0,0)O(0,0) to the point P(15,8)P(15, 8)
Distance OP=17OP = 17
Using the distance formula in the coordinate plane: OP=(150)2+(80)2=225+64=17OP = \sqrt{(15-0)^2 + (8-0)^2} = \sqrt{225 + 64} = 17.
3
Apply the Pythagorean theorem to the right triangle OTP\triangle OTP
Length PT=15PT = 15
Since the tangent line PTPT is perpendicular to the radius OTOT at the point of tangency TT, OTP\triangle OTP is a right triangle with hypotenuse OP=17OP = 17 and leg OT=8OT = 8. Thus, PT=OP2OT2=17282=15PT = \sqrt{OP^2 - OT^2} = \sqrt{17^2 - 8^2} = 15.

Key Concept

Tangent lines to circles and the Pythagorean theorem in the coordinate plane
Question 608Question

In the xyxy-plane, the graph of the equation x2+y28x+6y11=0x^2 + y^2 - 8x + 6y - 11 = 0 is a circle. If the center of the circle is (h,k)(h, k) and the radius is rr, what is the value of h+k+rh + k + r?

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Answer: 7

Answer

7
To find h+k+rh + k + r, we convert the general equation x2+y28x+6y11=0x^2 + y^2 - 8x + 6y - 11 = 0 to standard form (xh)2+(yk)2=r2(x - h)^2 + (y - k)^2 = r^2 by completing the square. Grouping terms gives (x28x)+(y2+6y)=11(x^2 - 8x) + (y^2 + 6y) = 11. Adding 16 and 9 to both sides to complete the square yields (x28x+16)+(y2+6y+9)=11+16+9(x^2 - 8x + 16) + (y^2 + 6y + 9) = 11 + 16 + 9, which simplifies to (x4)2+(y+3)2=36(x - 4)^2 + (y + 3)^2 = 36. Comparing this to the standard form gives center (h,k)=(4,3)(h, k) = (4, -3) and radius r=36=6r = \sqrt{36} = 6. The sum of these values is 4+(3)+6=74 + (-3) + 6 = 7.

Step-by-Step Solution

1
Group the variable terms and move the constant term to the right side of the equation.
(x28x)+(y2+6y)=11(x^2 - 8x) + (y^2 + 6y) = 11
To arrange the equation for completing the square.
2
Complete the square for both variables by adding the square of half the coefficient of the linear terms to both sides.
(x28x+16)+(y2+6y+9)=11+16+9(x^2 - 8x + 16) + (y^2 + 6y + 9) = 11 + 16 + 9
This creates factorable perfect square trinomials on the left side while maintaining equality.
3
Factor the perfect square trinomials and add the constants on the right side.
(x4)2+(y+3)2=36(x - 4)^2 + (y + 3)^2 = 36
To write the equation in the standard form of a circle: (xh)2+(yk)2=r2(x - h)^2 + (y - k)^2 = r^2.
4
Determine the coordinates of the center (h,k)(h, k) and the radius rr from the standard form.
Center coordinates h=4h = 4, k=3k = -3, and radius r=6r = 6
Comparing (x4)2+(y+3)2=36(x - 4)^2 + (y + 3)^2 = 36 to standard form reveals h=4h = 4, k=3k = -3, and r=36=6r = \sqrt{36} = 6.
5
Sum the values of hh, kk, and rr together.
4 + (-3) + 6 = 7
To find the final requested value.

Key Concept

Converting the general equation of a circle into standard form by completing the square to identify its center and radius.
Question 609Question

In the xyxy-plane, the graph of the equation x2+y212x+10y+k=0x^2 + y^2 - 12x + 10y + k = 0, where kk is a constant, is a circle. If this circle is tangent to the yy-axis, what is the value of kk?

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Answer: 25

Answer

The value of kk is 25.
Completing the square for the equation x2+y212x+10y+k=0x^2 + y^2 - 12x + 10y + k = 0 yields standard form (x6)2+(y+5)2=61k(x - 6)^2 + (y + 5)^2 = 61 - k. The center of the circle is (6,5)(6, -5) and the radius squared is r2=61kr^2 = 61 - k. Since the circle is tangent to the yy-axis (the line x=0x = 0), its radius must be equal to the horizontal distance from the center to the yy-axis, which is the absolute value of the xx-coordinate of the center, 6=6|6| = 6. Therefore, the radius is 66, and the radius squared is r2=36r^2 = 36. Setting 61k=3661 - k = 36 gives k=25k = 25.

Step-by-Step Solution

1
Complete the square for xx and yy variables in the equation.
(x6)2+(y+5)2=61k(x - 6)^2 + (y + 5)^2 = 61 - k
Completing the square allows the general form equation of the circle to be written in standard form, where the center and radius are easily identifiable.
2
Determine the center and the expression for the radius squared from the standard form.
Center is (6,5)(6, -5) and r2=61kr^2 = 61 - k
In the standard circle equation (xh)2+(ykc)2=r2(x - h)^2 + (y - k_c)^2 = r^2, the center is (h,kc)(h, k_c) and the right side represents the radius squared.
3
Relate the tangency condition to the radius of the circle.
r=6r = 6
A circle tangent to the yy-axis has its radius equal to the distance from its center to the line x=0x = 0, which is the absolute value of the center's xx-coordinate.
4
Calculate the value of the constant kk.
k=25k = 25
Since r=6r = 6, then r2=36r^2 = 36. Setting 61k=3661 - k = 36 and solving for kk gives k=25k = 25.

Key Concept

Completing the square to find the standard form of a circle's equation and applying geometric tangency properties to determine coordinates or constants.
Question 610Question

In right triangle PQRPQR, the measure of angle PQRPQR is 9090^\circ. Point SS lies on side PQPQ. If the length of side QRQR is 1515, the length of segment SRSR is 1717, and the length of segment PSPS is 1212, what is the length of side PRPR?

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Answer: 25

Answer

The length of side PRPR is 2525.
First, the Pythagorean theorem is applied to the smaller right triangle SQRSQR to solve for the unknown leg QSQS: QS=SR2QR2=172152=8QS = \sqrt{SR^2 - QR^2} = \sqrt{17^2 - 15^2} = 8. Next, the total length of leg PQPQ is the sum of its parts, PSPS and QSQS, which gives PQ=12+8=20PQ = 12 + 8 = 20. Finally, the Pythagorean theorem is applied to the main right triangle PQRPQR to find the hypotenuse PRPR: PR=PQ2+QR2=202+152=400+225=625=25PR = \sqrt{PQ^2 + QR^2} = \sqrt{20^2 + 15^2} = \sqrt{400 + 225} = \sqrt{625} = 25.

Step-by-Step Solution

1
Use the Pythagorean theorem on the right triangle SQRSQR to find the length of segment QSQS.
QS=8QS = 8
Triangle SQRSQR shares the right angle at QQ with triangle PQRPQR. Thus, QS2+QR2=SR2    QS2+152=172    QS=8QS^2 + QR^2 = SR^2 \implies QS^2 + 15^2 = 17^2 \implies QS = 8.
2
Determine the length of side PQPQ.
PQ=20PQ = 20
Since SS lies on side PQPQ, the length of PQPQ is the sum of PSPS and QSQS: PQ=12+8=20PQ = 12 + 8 = 20.
3
Use the Pythagorean theorem on right triangle PQRPQR to calculate the length of the hypotenuse PRPR.
PR=25PR = 25
PQ2+QR2=PR2    202+152=PR2    400+225=625    PR=25PQ^2 + QR^2 = PR^2 \implies 20^2 + 15^2 = PR^2 \implies 400 + 225 = 625 \implies PR = 25.

Key Concept

Multi-step application of the Pythagorean theorem in nested right triangles
Question 611Question

An isosceles trapezoid has a shorter base of length 1010, a longer base of length 2222, and a height of 88. What is the perimeter of the trapezoid?

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Answer: 52

Answer

The perimeter of the trapezoid is 5252.
To find the perimeter of the isosceles trapezoid, we first determine the length of the two congruent slanted sides. By drawing altitudes from the endpoints of the shorter top base to the longer bottom base, we create two right triangles at the sides of the trapezoid. The vertical leg of each right triangle is equal to the height of the trapezoid (88). The horizontal leg of each right triangle is equal to half the difference between the two base lengths, which is 22102=6\frac{22 - 10}{2} = 6. Applying the Pythagorean theorem, the length of each slanted side is 62+82=10\sqrt{6^2 + 8^2} = 10. Finally, the perimeter is the sum of all four sides: 10+22+10+10=5210 + 22 + 10 + 10 = 52.

Step-by-Step Solution

1
Calculate the horizontal base of the right triangles formed by drawing heights from the top base to the bottom base.
66
An isosceles trapezoid is symmetrical. Drawing vertical lines representing the height of 88 from the endpoints of the shorter base of length 1010 down to the longer base of length 2222 divides the longer base into a middle segment of length 1010 and two equal end segments. The length of each end segment is 22102=6\frac{22 - 10}{2} = 6.
2
Use the Pythagorean theorem to find the length of the slanted legs of the trapezoid.
1010
Each slanted leg is the hypotenuse of a right triangle with legs of length 66 and 88. According to the Pythagorean theorem, the hypotenuse length is 62+82=36+64=100=10\sqrt{6^2 + 8^2} = \sqrt{36 + 64} = \sqrt{100} = 10.
3
Find the perimeter of the trapezoid by adding the lengths of all four sides.
5252
The perimeter is the sum of the shorter base (1010), the longer base (2222), and the two slanted legs (each of length 1010). Therefore, the perimeter is 10+22+10+10=5210 + 22 + 10 + 10 = 52.

Key Concept

Applying the Pythagorean theorem to find missing side lengths in composite geometric figures
Question 612Question

In the xyxy-plane, triangle ABCABC is a right triangle with the right angle at BB. The vertices of the triangle are A(3,11)A(3, 11), B(15,20)B(15, 20), and C(27,y)C(27, y), where yy is a constant. If the length of the hypotenuse ACAC is 25 and y<20y < 20, what is the value of yy?

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Answer: 4

Answer

The value of yy is 4.
Applying the distance formula to vertices A(3,11)A(3, 11) and B(15,20)B(15, 20) yields a length of 15 for side ABAB. Since triangle ABCABC has its right angle at BB, the hypotenuse is AC=25AC = 25. Using the Pythagorean theorem (AB2+BC2=AC2AB^2 + BC^2 = AC^2), we find that BC=20BC = 20. Setting the distance between B(15,20)B(15, 20) and C(27,y)C(27, y) equal to 20 gives (2715)2+(y20)2=202(27-15)^2 + (y-20)^2 = 20^2. This simplifies to (y20)2=256(y-20)^2 = 256, which has solutions y=36y = 36 or y=4y = 4. Given that y<20y < 20, the value of yy must be 4.

Step-by-Step Solution

1
Calculate the length of segment ABAB using the distance formula.
AB=15AB = 15
To find one of the leg lengths of the right triangle.
2
Apply the Pythagorean theorem to find the length of leg BCBC.
BC=20BC = 20
To determine the length of the other leg of the right triangle.
3
Use the distance formula for BCBC and the condition y<20y < 20 to solve for yy.
y=4y = 4
To find the vertical coordinate of vertex CC.

Key Concept

Using the Pythagorean theorem in coordinate geometry to solve for unknown coordinates.
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