Question
Show from first principles that the function cos is differentiable at $\pi / 2$ and its derivative at $\pi / 2$ is $-1$.
Step 1
Step 1: Recall the definition of the derivative from first principles: The derivative of a function f(x) at a point x=a is given by: f'(a) = lim (h -> 0) [(f(a + h) - f(a))/h] Show more…
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