Find the general solution or the general expression for all angles, whose cosine is zero.
Find general value of x, when cos x = cos y
We have cosx = cosy or cosx - cosy = 0
either
or
either
or
where
either
or
where
either
or
, where
where
Hence, the general solution is
COROLLARY: If secx = secy cosx = cosy
So, when secx = secy, the general solution of where