One way in which to approach this proof would be to convert
1 (cos x)^2
------------- into ---------------- . Next, note that 1 - (sin x)^2 = (cos x)^2
(tan x)^2 (sin x)^2 and that 1 - (cos x)^2 = (sin x)^2.
Then we have:
(cos x)^2 (cos x)^2
------------- = -------------------- which is a true equation
(sin x)^2 (sin x)^2
