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Zorluk: OrtaRight Triangles and the Pythagorean Theorem

In right triangle PQRPQR, the measure of angle QQ is 9090^\circ. If sin(P)=513\sin(P) = \frac{5}{13} and the length of side QRQR is 1515, what is the length of side PQPQ?

Cevap: 36

Cevap

The length of side PQPQ is 3636.
By definition, sin(P)=oppositehypotenuse=QRPR\sin(P) = \frac{\text{opposite}}{\text{hypotenuse}} = \frac{QR}{PR}. Given that sin(P)=513\sin(P) = \frac{5}{13} and QR=15QR = 15, we set up the equation 513=15PR\frac{5}{13} = \frac{15}{PR} and solve for the hypotenuse PRPR, giving PR=39PR = 39. Using the Pythagorean theorem, PQ2+QR2=PR2PQ^2 + QR^2 = PR^2, we substitute the known values: PQ2+152=392    PQ2+225=1521    PQ2=1296PQ^2 + 15^2 = 39^2 \implies PQ^2 + 225 = 1521 \implies PQ^2 = 1296. Taking the square root of both sides gives PQ=36PQ = 36. Alternatively, recognizing that the sides of the triangle form a 55-1212-1313 Pythagorean triple scaled by a factor of 33 (since QR=5×3=15QR = 5 \times 3 = 15 and PR=13×3=39PR = 13 \times 3 = 39), the remaining leg PQPQ must be 12×3=3612 \times 3 = 36.

Adım Adım Çözüm

1
Set up the sine ratio for angle PP to find the length of the hypotenuse PRPR.
PR=39PR = 39
Since sin(P)\sin(P) is the ratio of the opposite side (QRQR) to the hypotenuse (PRPR), we can solve the equation 513=15PR\frac{5}{13} = \frac{15}{PR} to find that PR=39PR = 39.
2
Apply the Pythagorean theorem to solve for the length of side PQPQ.
PQ=36PQ = 36
In right triangle PQRPQR, the relationship between the sides is PQ2+QR2=PR2PQ^2 + QR^2 = PR^2. Substituting QR=15QR = 15 and PR=39PR = 39 gives PQ2+152=392PQ^2 + 15^2 = 39^2, which simplifies to PQ2=1296PQ^2 = 1296, so PQ=36PQ = 36.

Anahtar Kavram

Using trigonometric ratios to find side lengths of right triangles followed by the Pythagorean theorem.

Alternatif Yöntem

Recognize that the triangle's sides must be a multiple of the common 55-1212-1313 Pythagorean triple. Since the opposite side is 1515 (5×35 \times 3) and the hypotenuse is 3939 (13×313 \times 3), the scaling factor is 33, meaning the adjacent side PQPQ is 12×3=3612 \times 3 = 36.
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