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Math Help - [SOLVED] quick differentiation

  1. #1
    PIR
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    [SOLVED] quick differentiation

    does dy/dt of 2.5sin((pi)t/12) = 2.5cos((pi)t/12)?
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    Quote Originally Posted by PIR View Post
    does dy/dt of 2.5sin((pi)t/12) = 2.5cos((pi)t/12)?
    No

    The derivative of 2.5 \sin \left(\frac{\pi t}{12}\right) is \frac{2.5\:\pi}{12}\:\cos \left(\frac{\pi t}{12}\right)

    The derivative of f(ax+b) is : a f'(ax+b)
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  3. #3
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    Quote Originally Posted by PIR View Post
    does dy/dt of 2.5sin((pi)t/12) = 2.5cos((pi)t/12)?
    No it doesn't. You need to apply the chain rule on that \frac{\pi t}{12}

    Remember that by the chain rule if f(x) = Asin(wt) then f'(x) = Awcos(wt)
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  4. #4
    PIR
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    Thank you you two. Maths in the morning doesn't work for me I really should have picked up the chain...
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  5. #5
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    Quote Originally Posted by PIR View Post
    does dy/dt of 2.5sin((pi)t/12) = 2.5cos((pi)t/12)?
    Use the chain rule.

     \frac{d}{dt} K \sin( Rt) = KR\cos(Rt)


    Where K and R are constants.
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