Mathematics

Mathematics

Problem

For the function h(x)=sin⁡x−xcos⁡xh(x)=\sin x- x\cos x in the interval (0,2π)(0,2\pi), list all its local extrema in ascending order of their function values.
Intuitive explanation

The key is to find where h′(x)=0h'(x) = 0 by recognizing that the derivative simplifies nicely. Once you compute h′(x)=cos⁡x−cos⁡x+xsin⁡x=xsin⁡xh'(x) = \cos x - \cos x + x\sin x = x\sin x, you'll see that critical points occur when x=0,π,2πx = 0, \pi, 2\pi (the boundaries and where sin⁡x=0\sin x = 0). Evaluate hh at each interior critical point and any boundary behavior to identify which are actual local extrema, then order them by their yy-values rather than their xx-coordinates.

Intuitive explanation

The key is to find where h′(x)=0h'(x) = 0 by recognizing that the derivative simplifies nicely. Once you compute h′(x)=cos⁡x−cos⁡x+xsin⁡x=xsin⁡xh'(x) = \cos x - \cos x + x\sin x = x\sin x, you'll see that critical points occur when x=0,π,2πx = 0, \pi, 2\pi (the boundaries and where sin⁡x=0\sin x = 0). Evaluate hh at each interior critical point and any boundary behavior to identify which are actual local extrema, then order them by their yy-values rather than their xx-coordinates.

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