Need help with calculus. My teacher website is down and this is due at midnight. Problem in comments

Question

anonymous · Answer

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misty1212 · Answer

you can do this without calculus, calculus only makes it worse
the biggest cosine can be is 1, the smallest is $-1$

anonymous · Answer

Okay I didn't think about it that way

misty1212 · Answer

http://www.wolframalpha.com/input/?i=2 \cos%28x%29+domain+-3pi%2F2..+3pi%2F2

misty1212 · Answer

largest it can be is $2$ if $x=0$ and smallest is $-2$ if $x=\pi$ or $-\pi$

solomonzelman · Answer

I don't want to do the derivative test right now, nor do I want to do an observation based on 2nd derivative. I might as well just give you a good graphing calculator to graph the f(x), since I am done with math for now. https://www.desmos.com/calculator