Question

Help ASAP!! A triangle has side lengths of 11in, 15in, and 20in. Find the angle measures of the triangle. Round decimal answers to the nearest tenth. Someone help pls.

Answer 1

Answer:

<A = 47.7°

<B = 99.4°

<C = 32.9

Step-by-step explanation:

When given the measurements of all three sides, you can calculate the angles using the Cosine Law.

c² = a² + b² - 2ab cos C

(based on Pythagorean Theorem)

If we say: a = 15

b = 20

c = 11

11² = 15² + 20² - 2(15)(20) cos C

121 = 625 - 2(15)(20) cos C

121 = 625 - 600 cos C

⁻504 = ⁻600 cos C

cos⁻¹ (504 ÷ 600) = C

< C = 32.9°

a² = b² + c² - 2bc cos A

15² = 20² + 11² - 2(20)(11) cos A

225 = 521 - 2(20)(11) cos A

225 = 521 - 440 cos A

⁻296 = ⁻440 cos A

cos⁻¹ (296 ÷ 440) = A

<A = 47.7°

Then, since we know the sum of all three angles of a triangle equals 180°:

180° - 32.9° - 47.7° = 99.4°

<B = 99.4°