1.∫sec^2 (4x+1)dx; u=4x+1

2.∫ root(sin pi theta) cos(pi theta) d(theta); u= sin(pi theta)

3.∫ e^x dx /(1+e^x); u= 1+e^x

For #1, tan^4(4x+1)/4 +c..is the answer..but I don't get why tan should be ^4??

I took the deriv. of the u and replace dx with the stuff that only contains du..not dx...

And then,,I sometimes have problems solving some questions..

Please help!