integrate the following using trigonometric identities and/or substitutions:
x^2 + 1 / sqrt (9 - x^2) dx
x^3 / sqrt (x^2 + 4) dx
(tan x)^5 * (sec x)^6 dx
(cos x)^5 / sqrt (sin x) dx
with the first two i started out confidently but ended up wasting half an hour trying o figure them out .... and the last two are just impossible ...