(the 2nd derivative being <0 verifies that the turning point is a local maximum,
however you need to ensure the point you choose is to the right of the 2nd derivative =0).
Sinx=0 if x=0 or
Both sinx and x are positive or zero from x=0 to
hence the graph rises to a maximum and falls to zero.
You could simply choose x=2 as an alternative to