Question

Solve the triangle. B = 36°, a = 38, c = 18

Answer 1

Answer:

A ≈ 119.7°, b ≈ 25.7, C ≈ 24.3°

Step-by-step explanation:

A suitable app or calculator does this easily. (Since you're asking here, you're obviously not unwilling to use technology to help.)

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Given two sides and the included angle, the Law of Cosines can help you find the third side.

... b² = a² + c² - 2ac·cos(B)

... b² = 38² + 18² -2·38·18·cos(36°) ≈ 661.26475

... b ≈ 25.715

Then the Law of Sines can help you find the other angles. It can work well to find the smaller angle first (the one opposite the shortest side). That way, you can tell if the larger angle is obtuse or acute.

... sin(C)/c = sin(B)/b

... C = arcsin(c/b·sin(B)) ≈ 24.29515°

This angle and angle B add to less than 90°, so the remaining angle is obtuse. (∠A can also be found as 180° - ∠B - ∠C.)

... A = arcsin(a/b·sin(B)) ≈ 119.70485°