Solve cos(x)=−0.9 precalculus

Question

Solve  on 

There are two solutions, A and B, with A < B 

A = 

  B =  

 Give your answers accurate to 3 decimal places

Answer 1

154.158 degrees = A = .8564 pi radians

205.842 degrees = B = 1.244 pi radians

answer is 180+ or - 25.842 = 205.842, or 154.158

plug .9 into an inverse cosine function on a calculator to get 25.842= reference angle. convert degrees to radians by multiplying by pi/180