Find all solutions in [0,2𝜋) cos 4𝑥 = − √2/2

Answer 1

4x = -315, -135, 45, 225, 405 585, 765, 945, 1125, 1305, 1485, ...

x = 45/4 = 10.25, 225/4 = 56.25, 405/4 = 101.25, 584/4 = 146.25, 765/4 = 191.25, 945/4 = 236.25, 1125/4 = 281.25, 1305/4 = 326.25, 1485/4 = 371.25

only x = 11.25, 56.25, 101.25, 146.25, 191.25, 236.25, 281.25, 326.25, are 0<x<2pi

x= 11.25 + 45n where n = any integer, -1<n<8, n=0,1,2,3,4,5,6 or 7

or

x = pi/16 = npi/4 where n= any integer -1<n<8