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## Homework Statement

Use the definition of the derivative to show f is differentiable at x = 2.

f(x) = 1 + cos(pix/2)

## The Attempt at a Solution

I started getting the solution but got stuck at one part.

f`(x) = lim h->0 | [ f(x+h) - f(x) ] / (h)

= lim h->0 | [f(2+h) - f(2) ] / (h)

= lim h -> 0 | [1 + cos(pi(2+h)/2) - 0 ] / (h)

= lim h -> 0 | [1 + cos(2pi+hpi)/2 ] / (h)

I know im supposed to get the h's to cancel out but im having trouble getting there

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