# Calculus integration (hard)

• December 14th 2012, 12:04 AM
asilvester635
Calculus integration (hard)
Do I use integration by substitution?? this is a really tricky question for me
• December 14th 2012, 12:35 AM
MarkFL
Re: Calculus integration (hard)
Yes, try the substitution:

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

Then use:

$\sec(u)\tan(u)=\frac{d}{du}(sec(u))$
• December 14th 2012, 10:06 AM
asilvester635
Re: Calculus integration (hard)
LOL so the final answer is sec(1-x)... wow it's that easy...
• December 15th 2012, 12:07 AM
MarkFL
Re: Calculus integration (hard)
Not quite that easy...you need to correctly substitute for the differential to get:

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