You need to solve for sinx+xcosx=0.

(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