The Student Room Group

Integration by substitution

Can someone tell me why this integral equals secx^2 and not tanx^2?

I think it involved the identity '1+tanx^2=sec^2' but don't know why as there is no '1' in the answer?

Please could someone help :frown:
Reply 1
Original post by Katiee224
Can someone tell me why this integral equals secx^2 and not tanx^2?

I think it involved the identity '1+tanx^2=sec^2' but don't know why as there is no '1' in the answer?

Please could someone help :frown:


it is equals to both
(differs by a constant)
Reply 2
Original post by TeeEm
it is equals to both
(differs by a constant)


So you're saying as we don't know the constant C, then it could be equal to either?

The answer I get is to be used to solve an integration by parts question, so how do I know which answer to use?

Thanks :smile:
Reply 3
Original post by Katiee224
So you're saying as we don't know the constant C, then it could be equal to either?

The answer I get is to be used to solve an integration by parts question, so how do I know which answer to use?

Thanks :smile:


It is the same answer
I would have done it as tan2x too

tan2x + C = (sec2x - 1) + D

i.e they are not the same constants
Reply 4
Original post by TeeEm
It is the same answer
I would have done it as tan2x too

tan2x + C = (sec2x - 1) + D

i.e they are not the same constants


So tanx^2 would be a valid answer?
Reply 5
Original post by Katiee224
So tanx^2 would be a valid answer?


absolutely
Reply 6
Original post by TeeEm
absolutely


thank youuuuuuuuuu
Reply 7
Original post by Katiee224
thank youuuuuuuuuu

no worries

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