Solving Trig Equations Intro

Question

Solve cos(x)=-0.57 on 0≤ x< 2Π

The two solutions rounded to 4 decimal places are 

Answer 1

x is in the 2nd or 3rd quadrants where cosines <0

use a calculator with an inverse trig function

reference angle = 55.2498 degrees = 0.9643 radians

x= pi-0.9643 radians or pi+ 0.9643 radians

x = 3.1416+ or - 0.9643

x = 4.1059, 2.1773 radians

= 1.3069pi or -.6931pi

or

x = 180 + or - 55.2498

= 235.2498 or 124.7502 degrees