Year 12s: what will be the first way you research your future options? >>

Year 12s: what will be the first way you research your future options? >>

Year 12s: what will be the first way you research your future options? >>

Help with C4 Question...

Hi,
I'm currently doing OCR C4 Jan 09 and am having some difficulty with quesiton 4.
It is to find the answer to the integration with limits 1/4 pi and 0 of (1 + sinx)^2.
I've looked at the mark scheme but it just confused me more...
If someone can talk me through how to do it, that'd be awesome :smile:

:smile:

Thanks.

Study Forum Helper

You need to start with the identity

\cos 2x = \cos^2 x - \sin^2 x

Get

\sin^2 x

in terms of

\cos 2x

and so on.

OP

Original post by Mr M

You need to start with the identity

\cos 2x = \cos^2 x - \sin^2 x

Get

\sin^2 x

in terms of

\cos 2x

and so on.

Surely first I expand (1 + sinx)^2 to get 1 + 2sinx + sin^2x, then if I use that identity to sub out sin^2x I get 1 + 2sinx + 1/2(1 - cos2x)...

Study Forum Helper

Original post by El Xando

Surely first I expand (1 + sinx)^2 to get 1 + 2sinx + sin^2x, then if I use that identity to sub out sin^2x I get 1 + 2sinx + 1/2(1 - cos2x)...

If you like. That is correct.

OP

Original post by Mr M

If you like. That is correct.

I'm still not sure how that helps me integrate it to find an exact value :P

Study Forum Helper

Original post by El Xando

I'm still not sure how that helps me integrate it to find an exact value :P

Really? Presumably you know this ...

\int \cos (ax + b) = \frac{\sin(ax + b)}{a} + k

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