I need to show that two equations equal one another. It's too complicated to display fully on here but I'm stuck on a step:(adsbygoogle = window.adsbygoogle || []).push({});

dF/dr = df/dx cos2(h) + df/dy sin(h)

(dF/dr)^2 = (df/dx)^2 cos^2(h) + (df/dy)^2 sin^2(h)

Does anybody know how to get rid of the cos squared and sin squared?

P.S. By (dF/dr)^2 I mean the first derivative squared not the second derivative

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# Homework Help: Trig step in a chain rule question

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