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# c4 integration watch

1. how do i integrate cos2x / (3 + sin2x)??

i did this:
y= ln (3 +sin2x)

dy/dx = 1 / (3 + sin2x) * cos 2x

so answer is ln ( 3+ sin2x)

but actual answer is 0.5 ln ( 3 + sin2x) , and im not sure where the half came from.
2. Whenever you see an integral like this you must differentiate the bottom which is what you did. When you differentiate the sin2x you get 2cos2x which means the top is half the differential of the bottom hence the half before the log.
3. ah yes, silly mistake, cheers
4. No problem !

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Updated: April 13, 2006
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