Question: Max value of a continuous function on an interval.

I'm looking for a simple method of finding the maximum of a continuous function on a specific interval. I've thought about just checking endpoints and critical points on the interval... or discretizing the function on the interval in an array and doing it numerically... Or is there a quicker method I'm missing perhaps? The application is: I've got a complex rational function in the Laplace domain corresponding to an analog filter and I need a way of knowing the 3dB frequency, and to do that I need the max.
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