does dy/dt of 2.5sin((pi)t/12) = 2.5cos((pi)t/12)?
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Originally Posted by PIR does dy/dt of 2.5sin((pi)t/12) = 2.5cos((pi)t/12)? No The derivative of $\displaystyle 2.5 \sin \left(\frac{\pi t}{12}\right)$ is $\displaystyle \frac{2.5\:\pi}{12}\:\cos \left(\frac{\pi t}{12}\right)$ The derivative of f(ax+b) is : a f'(ax+b)
Originally Posted by PIR 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 $\displaystyle \frac{\pi t}{12}$ Remember that by the chain rule if $\displaystyle f(x) = Asin(wt)$ then $\displaystyle f'(x) = Awcos(wt)$
Thank you you two. Maths in the morning doesn't work for me I really should have picked up the chain...
Originally Posted by PIR does dy/dt of 2.5sin((pi)t/12) = 2.5cos((pi)t/12)? Use the chain rule. $\displaystyle \frac{d}{dt} K \sin( Rt) = KR\cos(Rt) $ Where K and R are constants.
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