integration substitution :(

can some one help me please , how do you work out C?

Split it into 3 sections.

1 - Replace the root 1 + tan with u^2.

2 - Rearrange u^2 to find out what tan equals

3 - Differentiate the u^2 = 1 + tan (implicitly) and you should get a way of getting replacing the sec^2 with a U and replacing the dx with a du.

Does that make sense (I don't just want to give you the answer) but I hope that helped.