Posted by **Anonymous** on Friday, July 6, 2012 at 9:26pm.

Use the 2nd derivative test to find the extremer of f on the interval [0,2PI]

f(x)=2cosx+sin 2x

- calculus -
**Anonymous**, Friday, July 6, 2012 at 9:49pm
Ack, I forgot, I don't seem to have a problem with numbers but when it comes to the sin and cos...I am not sure how to derive them. I want to say that 2cosx would end up being something like 2-sinx (x)...but then I feel like there's something wrong w/that scenario.

- calculus -
**Reiny**, Friday, July 6, 2012 at 10:47pm
first derivative:

-2sinx + 2cos 2x

2nd derivative:

-2cosx - 4sin 2x

take it from there

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