intergral(tanx(secx)^2,x)

my book tells me to make u = sec(x) du = tanxsecx dxwhich makes sense, but could you also make u = tanx making du = (secx)^2 dx? But the latter method is incorrect why?

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- Feb 18th 2009, 08:49 PMs3n4teConfused about this trig substitution!
intergral(tanx(secx)^2,x)

my book tells me to make u = sec(x) du = tanxsecx dxwhich makes sense, but could you also make u = tanx making du = (secx)^2 dx? But the latter method is incorrect why? - Feb 18th 2009, 08:54 PMmr fantastic
- Feb 18th 2009, 08:58 PMmollymcf2009
- Feb 18th 2009, 09:00 PMs3n4te
When I graphed both functions they aren't the same, is that normal?

- Feb 18th 2009, 09:12 PMmollymcf2009
- Feb 18th 2009, 09:17 PMs3n4te
oh that make sense :P

thanks