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## Main Question or Discussion Point

How can I use trig identities to let me differentiate [itex]\sin \left ( x + \frac{\pi}{2} \right)[/itex] and [itex]3 \sin x - 2 \cos x[/itex]?

- Thread starter cscott
- Start date

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How can I use trig identities to let me differentiate [itex]\sin \left ( x + \frac{\pi}{2} \right)[/itex] and [itex]3 \sin x - 2 \cos x[/itex]?

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TD

Homework Helper

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I don't see why you'd want to change the second one though, taking the derivative is lineair so [itex]\left( {3\sin x - 2\cos x} \right)^\prime = 3\left( {\sin x} \right)^\prime - 2\left( {\cos x} \right)^\prime [/itex]

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Damn, I guess I wasn't looking at them right. Thanks.

Hurkyl

Staff Emeritus

Science Advisor

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You don't need trig identities to differentiate those...

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