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Thread: Need help with trig again

  1. #1
    Dec 2007

    Need help with trig again

    Different problem. This time though, I have no idea where to start.

    sin^1/2 x cos x - sin^5/2 x cos x = cos^3 x [The square root of] sin x
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  2. #2
    Flow Master
    mr fantastic's Avatar
    Dec 2007
    Quote Originally Posted by mathgeek777 View Post
    Bumping this up, it is quite urgent as the assignment is due tomorrow.
    There are very good reasons for doing the following, sport:

    1. Don't bump (especially in the space of 30 minutes!!! - where's the fire??)
    2. Clearly state what the question is. Otherwise it must be guessed that you want to prove an identity.
    3. Learn some basic latex.
    4. Don't leave things to the last minute. Then it won't be so urgent. (And then you'll probably end up living longer - without ulcers).

    Left hand side $\displaystyle = \sqrt{\sin x} \cos x - \sin^2 x \sqrt{\sin x} \cos x\, ^*$

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

    = .......

    = Right hand side.

    $\displaystyle ^*\, $ $\displaystyle a^{5/2} = a^2 a^{1/2} = a^2 \sqrt{a}$
    Last edited by mr fantastic; Jan 7th 2008 at 04:31 PM. Reason: Added some humour to take the edge off my testiness
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