Explain how I can solve cos 5pi3 Explain how I can solve cos

Solution

given cos 5pi/3

PI=180

5*PI/3 = 300

300 degrees lies in the 4th quadrant where cos is positive. The reference angle is 60. Therefore, we want cos(60)

or cos(PI/3) =1/2

cos 5pi/3 = 1/2