Explanation:
csc x / (cot x + tan x)
Write in terms of sine and cosine.
(1 / sin x) / [(cos x / sin x) + (sin x / cos x)]
Multiply top and bottom by sin x.
1 / [cos x + (sin²x / cos x)]
Multiply top and bottom by cos x.
cos x / (cos²x + sin²x)
Use Pythagorean identity.
cos x / 1
cos x