What's Wrong With This Answer? 1 sec, posting the attached img. What's Wrong With This Answer? 1 sec, posting the attached img. @Mathematics

I double checked this, and I still don't see where the heck I went wrong.

did you take the derivaitve of the e^-x twice

i think you did

Where?

when you applied the product rule

No because that second -ve sign comes from the cos

because (cosx)' = -sinx

looks good to me if this is on line work, you probably have to write sin(pix) rather than sinpix

Aw these stupid technical errors.

http://www.wolframalpha.com/input/?i=d%2Fdx+log%282%2C+e^%28-x*cos%28pi*x%29%29%29

Why is the derivative log(2) in that link instead of ln(2)?

read the fine print...log is the natural log

the large print giveth and the small print taketh away

that wolfram link is not the question you were asked

If you mean the wolfram solution, it is ln(2) "log (x) is the natural logarithm"

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