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TomLikesPhysics
Group Title
I want to integrate 2sinx/[cosx]^3.
I wrote that as tanx/[cosx]^2 and saw that I now have to integrate f/f`. But somehow this does not help. Is there some formula I can use to integrate f/f`?
 2 years ago
 2 years ago
TomLikesPhysics Group Title
I want to integrate 2sinx/[cosx]^3. I wrote that as tanx/[cosx]^2 and saw that I now have to integrate f/f`. But somehow this does not help. Is there some formula I can use to integrate f/f`?
 2 years ago
 2 years ago

This Question is Closed

experimentX Group TitleBest ResponseYou've already chosen the best response.1
let cos x = u => sin x dx = du
 2 years ago

cibychak Group TitleBest ResponseYou've already chosen the best response.1
The given question comes out to be \[2\tan x \sec ^{2}x.dx\] which can be written as, \[\int\limits_{?}^{?}2\sec x.secx.tanx.dx\] now take secx=t, dt=secx.tanx then integrate
 2 years ago

TomLikesPhysics Group TitleBest ResponseYou've already chosen the best response.0
Hmm I just worked it out using substitution as experimentX suggested. I just thought since there is a "shortcut" to integrate f`/f as ln(f) that there is also a similar way to integrate f/f`. We have not (and will not) be introduced to secx in school so I guess it is not supposed to be the answer  also if it is right. Thx anyway cibychak and of course experimentX.
 2 years ago

cibychak Group TitleBest ResponseYou've already chosen the best response.1
not introduced to secx?
 2 years ago

TomLikesPhysics Group TitleBest ResponseYou've already chosen the best response.0
Yup. Somehow that is not part of the mathematicsclass in germany. I guess I hear about that kind of stuff when I go to university.
 2 years ago
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