To Find: General solution.

Given: cos x + sin x = 1 cos (x - ) = = cos( or cos()

[Divide on both sides and cos(x-y) = cos x cos y - sin x sin y]

Formula used: cos = cos = 2n

By using above formula, we have

x - = 2n x = 2n +

x = 2n + or x = 2n - where n I

So general solution is x = 2n + or x = 2n - where n I