Find all the solutions in the interval [0,2pi] of cosx=square root 2/2

The equation is cos(x) = sqrt(2)/2.

Since cos(x) = sqrt(2)/2, we know that x can be π/4, 7π/4, 3π/4, or 5π/4.

So, the solutions in the interval [0,2π] are x = π/4, 3π/4, 5π/4, and 7π/4.