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Maths help

B77E5C7C-9085-4277-880A-C3882F8C191A.jpg.jpeg
Can someone explain what went wrong here pls
Reply 1
Original post by Yazomi
B77E5C7C-9085-4277-880A-C3882F8C191A.jpg.jpeg
Can someone explain what went wrong here pls

You've done this before?
Substitution (reverse chain rule) at the start is the obvious way to go?

Your mistake is integrating tan^3. Get that sorted and it's correct, but long winded.
(edited 3 years ago)
Reply 2
Original post by mqb2766
You've done this before?
Substitution (reverse chain rule) at the start is the obvious way to go?

Your mistake is integrating tan^3. Get that sorted and it's correct, but long winded.

Ahhh I found the post yeah it was kind of similar. Still trying to get my head around all of this it's so much to remember/understand T^T. I'll have a try following that method thanks!
Reply 3
Original post by Yazomi
Ahhh I found the post yeah it was kind of similar. Still trying to get my head around all of this it's so much to remember/understand T^T. I'll have a try following that method thanks!

When you have
f^n(x)*g(x)
And g is the derivative of f, then it's almost a one liner to write down the integral (substitution / reverse chain rule). So get in the habit of spotting when the integrand is the product of two such terms.
(edited 3 years ago)
Reply 4
Original post by mqb2766
When you have
f^n(x)*g(x)
And g is the derivative of f, then it's almost a one liner to write down the integral (substitution / reverse chain rule). So get in the habit of spotting when the integrand is the product of two such terms.


Oh wait sorry I’m still a tad confused
71970D1B-CCE4-4369-B8B9-15A1E0F80414.jpg.jpeg this is where I got up to but I can’t figure out how they got just 1/2(sec^2x)
Reply 5
Original post by Yazomi
Oh wait sorry I’m still a tad confused
71970D1B-CCE4-4369-B8B9-15A1E0F80414.jpg.jpeg this is where I got up to but I can’t figure out how they got just 1/2(sec^2x)

Not quite sure what you're referring to, but note that tan^2x and sec^2x differ by a constant so either is acceptable (multiplied by 1/2) as the answer to the integral because of the constant of integration.

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