first derivatives test and trig functions

I am supposed to use the first derivative test to find any local min/max of on the interval

Take the derivative and get

Set the derivative = 0 and I get

I graphed both 2cos(x) and sin(x) and there are 2 intersections. How do I solve for x?

Thanks!

Re: first derivatives test and trig functions

Quote:

Originally Posted by

**baldysm** I am supposed to use the first derivative test to find any local min/max of

on the interval

Take the derivative and get

You have done the derivative incorrectly.

Re: first derivatives test and trig functions

Hey baldysm.

Hint: sin(x)/cos(x) = tan(x).

Edit: Also check HallsOfIvy's post above.