Find all solutions of the equation in the interval 0 2 pi En

Find all solutions of the equation in the interval [0, 2 pi]. (Enter your answer as a comma-separated list) cos 2x - cos sec = 0 Use a graphing utility so graph the equation and verify the solution

Solution

cos2x - cos5x =0

Plot the graph of y = cos2x and y = cos5x

Check for point of interecstions of two grapsh

we get : x= 2pi/3 , 2pi,0,8pi/7, 4pi/3, 2pi/7 , 12pi/7 , 10pi/7 , 4pi/7 , 6pi/7

graph 4 is correct