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reduction formulae for tan^n[x]

so i have to integrate
Unparseable latex formula:

tan^n(x)\dx



and this is what i have done so far

tann2(x)×(sec2(x)1)=tann2(x)×sec2(x)tann2(x)[br]\displaystyle\int tan^{n-2}(x) \times (sec^2(x) - 1) = \displaystyle\int tan^{n-2}(x) \times sec^2(x) - \displaystyle\int tan^{n-2}(x)[br]

so

In=tann2(x)×sec2(x)In2I_n = \displaystyle\int tan^{n-2}(x) \times sec^2(x) - I_{n-2}

how do i work with

tann2(x)×sec2(x)\displaystyle\int tan^{n-2}(x) \times sec^2(x)
Reply 1
Make a substitution, remembering that ddxtanx=sec2x\frac{d}{dx}\tan x = \sec^2x.
Can you not integrate by parts here? :s-smilie:
Reply 3
Well played.
Reply 4
Mathematician!
Can you not integrate by parts here? :s-smilie:


i tried that first but it just made it more complicated, anyway i got the answer with this [f(x)]m.f(x)dx=[f(x)](m+1)(m+1) \displaystyle\int [f(x)]^m . f'(x) dx = \frac{[f(x)]^{(m+1)}}{ (m + 1)}

would like to know how to do by parts if possible
rg2005
i tried that first but it just made it more complicated, anyway i got the answer with this [f(x)]m.f(x)dx=[f(x)](m+1)(m+1) \displaystyle\int [f(x)]^m . f'(x) dx = \frac{[f(x)]^{(m+1)}}{ (m + 1)}

would like to know how to do by parts if possible


Not sure, the recognition method is far better.
look in the K.A stroud book , mathematics for engineers 6th edition, shows it
Reply 7
Change sec^2x to 1 + tan^2x, you should get another I_n and a I_{n-2}

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