Use the Law of Cosines to solve the triangle. (Round your answers to two decimal places.)

Question

a = 1.42, b = 0.75, c = 1.25

A = _____°

B = _____°

C = _____°

Answer 1

Hi Aerin H.,

With a = 1.42, b = 0.75, and c = 1.25,

1.42² = 0.75² + 1.25² - 2*0.75*1.25*cos(A)

(1.42² - 0.75² - 1.25²)/(-2*0.75*1.25) = cos(A)

A = cos^-1[(1.42² - 0.75² - 1.25²)/(-2*0.75*1.25)]

A = 86.68^o

B = cos^-1[(0.75² - 1.42² - 1.25²)/(-2*1.42*1.25)]

B = 31.82^o

C = cos^-1[(1.25² - 1.42² - 0.75²)/(-2*1.42*.75)]

C = 61.50^o, (of course we could have found this by 180^o - 86.68^o - 31.82^o = 61.50^o)

I hope this helps, Joe.