Question

A=8, b=5, C=90 degree; Find c, A, and B

This is for the law of sine and cosine

Answer 1

• c = √89 ≈ 9.434

• A = arcsin(8/√89) ≈ 57.995°

• B = arcsin(5/√89) ≈ 32.005°

Explanation:

By the law of cosines, ...

c² = a² + b² -2ab·cos(C)

Since c=90°, cos(C) = 0 and this reduces to the Pythagorean theorem for this right triangle.

c = √(8² +5²) = √89 ≈ 9.434

Then by the law of sines (or the definition of the sine of an angle), ...

sin(A) = a/c·sin(C) = a/c = 8/√89

A = arcsin(8/√89) ≈ 57.995°

sin(B) = b/c·sin(C) = b/c = 5/√89

B = arcsin(5/√89) ≈ 32.005°