# integration questionWatch

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#1
use the identity secx^2= tanx^2 +1 and the substitution u=tanx to find
INT tanx^4

i think i have made a silly mistake in this. can someone share their solution with me please??
damn revision!!!!
0
13 years ago
#2
(Original post by realicetic)
use the identity secx^2= tanx^2 +1 and the substitution u=tanx to find
INT tanx^4

i think i have made a silly mistake in this. can someone share their solution with me please??
damn revision!!!!
Int tan^4x dx

= Int tan^2x sec^2x dx - Int tan^2x dx

= Int u^2 du - Int (sec^2x -1) dx

= u^3/3 - tanx + x + C

= 1/3 tan^3x - tanx + x + C
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