proving identity (1 Viewer)

maths lover · Mar 30, 2011

2cos cubedx - cos x
sinxcos squared x - sin cubed x is equal to cot x

SpiralFlex · Mar 30, 2011

$LHS = \frac{2\cos^ 3 x - \cos x}{\sin x \cos^2 x - \sin^3 x}$

$= \frac{\cos x(2\cos^2 x - 1)}{\sin x (\cos^2 x - \sin^2 x)}$

Remember the identities $\cos^2 x - \sin^2 x = \cos 2x$ and $2\cos^2 x - 1= \cos 2x$

So,

$= \frac{\cos x(\cos 2x)}{\sin x (\cos 2x)}$

$= \frac{\cos x}{\sin x}$

$= \cot x$

$= RHS$

maths lover · Mar 30, 2011

thanks man

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proving identity (1 Viewer)

maths lover

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SpiralFlex

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