4 sec²(x) = 8
Divide each side by 4: sec²(x) = 2
Take the square root of each side: sec(x) = + or - √2
We know that sec(x) = 1/cos(x)
So the equation becomes 1/cos(x) = + or - √2
Divide '1' by each side: cos(x) = + or - (1/2) √2
x = 45°, 135°, 225°, 315°
