for derivative sinx = cosx, by setting up into formal definition formula limΔx->0 [itex]\frac{f(x+Δx)-f(x)}{Δx}[/itex](adsbygoogle = window.adsbygoogle || []).push({});

this formal definition of derivative is formulated from the cartesian coordinate system where the horizontal is x and verticle is y. But sinx is a trig function and trig functions are represented on the graph where the horizontal is an angle.

So how does it make sense that trig functions can be set up into the formal definition of a derivative in the same manner as non-trig functions?

Meaning, how does this make sense? limΔx->0 [itex]\frac{sin(x+Δx)-sinx}{Δx}[/itex]

I know how to work it out and get cosx. But it doesn't seem to make as much sense visually as a nontrig proof.

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# Formal definition of derivative: trig vs non trig functions

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