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How do they integrate the first bit?

I'm aware you can use identities but when you do, don't you get:

1/4cos 2x

and cos 2x = 1 -2 sin²x

so should the answer be:

1/4 -1/2sin²x

(edited 12 years ago)

Reply 1

marcusmerehay

Sometimes you can use 'guess-and-check' to integrate.

What is the derivative of

y sin^2(x)

(w.r.t. x)?

Reply 2

0le

Original post by marcusmerehay

Sometimes you can use 'guess-and-check' to integrate.

What is the derivative of

y sin^2(x)

(w.r.t. x)?

I see what you mean and how they got their answer now, but why is my way wrong? What happens to the 1/4??

Reply 3

marcusmerehay

Original post by djpailo

I see what you mean and how they got their answer now, but why is my way wrong? What happens to the 1/4??

The 1/4 would be 'absorbed' by the integration constant, but the fact remains that you would have yet to integrate the expression in the first place, so it's irrelevant.

Reply 4

0le

Original post by marcusmerehay

The 1/4 would be 'absorbed' by the integration constant, but the fact remains that you would have yet to integrate the expression in the first place, so it's irrelevant.

Cool, I think I get it now thanks.

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