8313 Solve the equation on the interval 0s0 Solution16 cos2

8.3.13 Solve the equation on the interval 0s0

16 cos^2 theta = 4

dividing entire equation by 16

cos^2 theta = 4/16

cos^2 theta = 1 / 4

cos theta = + - 1/2

cos theta = 1/2 , theta = cos^-1 (1/2) , theta = pi/3 , 5pi/3

cos theta = -1/2 , theta = cos^-1 (-1/2) , theta = 2pi/3 , 4pi/3

solutions are

{ pi/3 , 5pi/3 , 2pi/3 , 4pi/3 }