The two sides of the triangle are 17 and 8, and the cosine of the angle between them is 15/17.
September 3, 2021 | education
| The two sides of the triangle are 17 and 8, and the cosine of the angle between them is 15/17. Find the area of this triangle.
It is known that cos2α + sin2α = 1. Knowing that cos α = 15/17, we can find sin α:
sin2α = 1 – cos2α = 1 – (15/17) ^ 2 = 1 – (225/289) = (289 – 225) / 289 = 64/289;
sinα = 8/17.
The area of a triangle is equal to half the product of the lengths of two sides by the sine of the angle between them:
S = 0.5 * a * b * sinα = 0.5 * 17 * 8 * 8/17 = 32.
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