# integrating over piecewise functions

by joshmccraney
Tags: functions, integrating, piecewise
 P: 112 given a function $f(x)$ that is piecewise smooth on interval $-L PF Patron HW Helper Sci Advisor P: 2,554  Quote by joshmccraney given a function [itex]f(x)$ that is piecewise smooth on interval $-L The latter. Suppose for example that ##f(x) = |x|^{1/2}##. This is smooth (infinitely differentiable) everywhere except at ##x = 0##, and f'(x) = \begin{cases} \frac{1}{2|x|^{1/2}} & \textrm{ if }x > 0 \\ \frac{-1}{2|x|^{1/2}} & \textrm{ if }x < 0 \\ \end{cases} As ##f'## is unbounded on ##[-L,L]##, it's necessary to use two (improper) integrals to integrate it: \lim_{a \rightarrow 0^-} \int_{-L}^{a} f'(x) dx + \lim_{b \rightarrow 0^+}\int_{b}^{L} f'(x) dx Both limits exist and the answers have opposite signs, so the result is 0.  also, am i correct that if [itex]f(x)$ is piecewise smooth, then $f'(x)$ is piecewise continuous but not necessarily piecewise smooth?
Assuming "smooth" means infinitely differentiable, ##f'## will be piecewise smooth. If by "smooth" you merely mean (once) differentiable, then ##f'## is not necessarily even piecewise continuous.
 P: 112 thanks for the reply. think i have it now.

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