Question

Difficulty: MediumPythagorean Theorem and Special Right Triangles

In right triangle XYZXYZ, Y=90\angle Y = 90^\circ and X=45\angle X = 45^\circ. The hypotenuse XZXZ has a length of 12212\sqrt{2} units. Point WW lies on leg XYXY such that XW=7XW = 7 units. What is the length, in units, of segment ZWZW?

  1. 1313Answer
  2. B
    119\sqrt{119}
  3. C
    1717
  4. D
    193\sqrt{193}
  5. E
    313\sqrt{313}

Answer

The length of segment ZWZW is 1313 units.
Because XYZ\triangle XYZ is an isosceles right triangle (45459045^\circ-45^\circ-90^\circ), its leg lengths XYXY and YZYZ are equal to the hypotenuse divided by 2\sqrt{2}, giving 1212. Segment YWYW is 127=512 - 7 = 5. In right triangle ZYW\triangle ZYW, the hypotenuse ZW=122+52=13ZW = \sqrt{12^2 + 5^2} = 13.

Step-by-Step Solution

1
Determine the leg lengths of XYZ\triangle XYZ using special right triangle properties.
XY=YZ=12XY = YZ = 12
In a 45459045^\circ-45^\circ-90^\circ right triangle, the hypotenuse is leg2\text{leg} \cdot \sqrt{2}. Given XZ=122XZ = 12\sqrt{2}, each leg length is 1212.
2
Calculate the length of segment YWYW.
YW=5YW = 5
Since point WW lies on leg XYXY and XW=7XW = 7, YW=XYXW=127=5YW = XY - XW = 12 - 7 = 5.
3
Apply the Pythagorean Theorem to right triangle ZYW\triangle ZYW to solve for hypotenuse ZWZW.
ZW=13ZW = 13
ZW=YZ2+YW2=122+52=144+25=169=13ZW = \sqrt{YZ^2 + YW^2} = \sqrt{12^2 + 5^2} = \sqrt{144 + 25} = \sqrt{169} = 13.

Key Concept

Properties of 45459045^\circ-45^\circ-90^\circ special right triangles and multi-step applications of the Pythagorean Theorem.
Estimated Time:1m 0s
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