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210 • Chapter 6: Examples from Calculus> evalf( sol );{−1.570796327 + 1.061275064 I,−1.570796327 − 1.061275064 I, 0.6662394321,2.475353222}In this example, only the real solutions are of interest. You can usethe select command to select the real constants from the solution set.> infl := select( type, sol, realcons );⎧ ⎛1 √⎞ ⎛11 √⎞ ⎫1⎪⎨5 − 5 − ⎪⎬infl :=⎪⎩ arctan ⎜⎝2 √ 2 2 ⎟ ⎜√ ⎠ , −arctan ⎝2 2 2 ⎟√ √ ⎠ + π−2 + 2 5 −2 + 2 5 ⎪⎭> evalf( infl );{0.6662394321, 2.475353222}You can see from the graph above that f2 actually does change signat these x-values. The set of inflection points is given by the following.> { seq( [x, f(x)], x=infl ) };