Answer to Question #36767 in Calculus for keith

Question

a) Find the critical points, if any, of the following function on the given interval.

b) Determine the absolute extreme values of f on the given interval.

c) Use a graphing utility to confirm your conclusions.

f(x)=sin(3x)on [−π4,π3]

I Know f′(x)=3cos(3x).

However, I'm not exactly sure how to determine the zeros for x for a trig function.

and even I know how to find the zeros of a cosine function I don't now what to do with them after that.

please if somebody can solve this I've been at it for over 5 hr's