# Math Help - Calculus integration (hard)

1. ## Calculus integration (hard)

Do I use integration by substitution?? this is a really tricky question for me

2. ## Re: Calculus integration (hard)

Yes, try the substitution:

$u=1-x\,\therefore\,du=-dx$

Then use:

$\sec(u)\tan(u)=\frac{d}{du}(sec(u))$

3. ## Re: Calculus integration (hard)

LOL so the final answer is sec(1-x)... wow it's that easy...

4. ## Re: Calculus integration (hard)

Not quite that easy...you need to correctly substitute for the differential to get:

$-\int\,d(\sec(u))=-\sec(u)+C=-\sec(1-x)+C$