Thread: Help with trig functions please
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Old May 17th, 2009, 11:25 AM
bobby bobby is offline
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Default Help with trig functions please
I need to know how

1-\cos(2\arcsin\frac{s}{4}) = \frac{s^{2}}{8}

and how

\sin(2\arcsin\frac{s}{4}) = 2\frac{s}{4}\sqrt{1-\frac{s^{2}}{16}}

I know the rule \cos\arcsin(x)) = \sqrt{1-x^{2}} but don't know what to do with the 2 before the inverse trig functions eah time.

Thanks
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