You need to solve the equation sin x = cos x to find the angle for the functions sine and cosine have equal values.
You need to remember that the functions sine and cosine do not cancel for the same angle, hence you may divide the equation by cos x such that:
`sin x/cos x = cos x/cos x =gt tan x = 1`
`x = tan^(-1) (1) + n*pi =gt x = (pi/4) + n*pi`
Hence, the functions sine and cosine have equal values at `x = pi/4 + n*pi` .