precalculus
posted by Ama .
Write the trigonometric expression in terms of sine and cosine, and then simplify.
cos u + sin u tan u

cos u + sin u (sin u/cos u)
cos u + sin^2 u / cos u
cos^2u/cos u + sin^2 u/cos u
(cos^2 u + sin^2 u) / cos u
1/cos u