Question

solve for x
cos(5x)+cos(2x)=0
all step
answer Pi/7 + 4pi/7 k, 3pi/7+ 4pi/7 k, pi/3 + 4pi/3 k, where k=1,2,3,4,....

Answer 1

cos 5x = -cos 3x = cos (pi + 3x)

Answer 2

Hint: Use \[\cos{C} + \cos{D} = 2\cos{\left(\frac{C+D}{2} \right)}\sin{\left(\frac{C-D}{2}\right)}\]

Answer 3

Can you show all the steps?