9: The second derivative is

Dividing points:

However, cos(x) = −2 is not possible and cos(x) = 1 is true only for x = 2kπ, which is not in the domain. Thus f ′′ is never zero.
Since y² + y − 2 < 0 for y = cos(x) from [−1,1), the numerator in f ′′ is always positive, the denominator also positive, so f ′′ > 0 on all intervals of the domain.
Thus f is concave up on all intervals of its domain.

No inflection points.

Now draw coordinate axes and mark all points and trends we learned so far.

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