Question

Integral of (−9sin(t)sec^2(cos(t))dt ?

Answer 1

put u= cos t
du =... ?

Answer 2

du = -sintdt

Answer 3

good,
so your integral,
9 sec^2 (cos t) (-sin t dt)
becomes, integral 9 sec^2u du
right ?

Answer 4

oh, i see now. thanks :)

Answer 5

cool, welcome ^_^