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#1 2008-09-06 22:14:20
- qweiop90
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- Registered: 2008-08-19
- Posts: 8
differentation
differentate :ln(sinx cos x) answer provided2 cot 2x)
cos x/ sinx - sin x / cos x
cos^2 x - sin^2 x/ cos x sin x
stucked
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#2 2008-09-06 23:55:23
- JaneFairfax
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- Registered: 2007-02-23
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Re: differentation
You can easily finish it off from here.
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#3 2008-09-06 23:57:16
- mathsyperson
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- Registered: 2005-06-22
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Re: differentation
Post collision aah
You're nearly there already. Using the trigonometric double angle formulae, you can turn your last expression into cos 2x / (1/2 sin 2x) = 2 (cos 2x / sin 2x) = 2 cot 2x.
You could have also used the double sine identity from the start, turning the original expression into ln(1/2 sin 2x) and differentiating from there.
Last edited by mathsyperson (2008-09-07 01:23:33)
Why did the vector cross the road?
It wanted to be normal.
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#4 2008-09-07 00:40:15
- JaneFairfax
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Re: differentation
You could have also used the double sine identity from the start, turning the original expression into 1/2 ln(sin 2x) and differentiating from there.
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#5 2008-09-07 01:24:50
- mathsyperson
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Re: differentation
That's what I get for not paying attention. 
Why did the vector cross the road?
It wanted to be normal.
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