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Mathematics 9 Online
Parth (parthkohli):

Nice problem if you see it.

TheSmartOne (thesmartone):

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Parth (parthkohli):

\[\tan n \theta = \frac{\binom{n}{1}t - \binom{n}{3}t^3 + \binom{n}5 t^5 + \cdots }{\binom{n}0 - \binom{n}2t^2 + \binom{n}4 t^4 + \cdots }\]where \(t = \tan \theta \).

OpenStudy (anonymous):

Woah...

OpenStudy (anonymous):

agree ...and wat do u haveto solve for?

Parth (parthkohli):

believe me, it's really obvious if you see the solution.

OpenStudy (flvskidd):

n6 n7 t6 t7

ganeshie8 (ganeshie8):

The formulas for \(\cos(n\theta)\) and \(\sin(n\theta)\) follow trivially from de moivre's theorem : \[\cos(n\theta)+i\sin(n\theta)=(\cos\theta+i\sin\theta)^n \] expand right hand side and compare real and imaginary parts to get

ganeshie8 (ganeshie8):

next, \(\tan(n\theta) = \dfrac{\sin(n\theta)}{\cos(n\theta)}\), and simplifying should do...

Parth (parthkohli):

yeah haha

ganeshie8 (ganeshie8):

to reach your formula, i think we need to divide top and bottom by \(\cos^n\theta\)

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