What Went Wrong Here? Calculus Homework

First time taking Calculus in a while and we're working on integration by substitution right now. Here's the problem and work done: http://imgur.com/7JEYmBf
According to WebAssign the answer is supposed to be -(2/21)(cos(7t))^(3/2)+c but I can't figure out where I dropped the negative and it's pissing me off. Normally I wouldn't ask basil, but I've got a short quiz tomorrow and it's too late to go into tutoring hours. ;_;

Thanks.

January 21, 2014

3 Comments • Newest first

ChildsPlay

[quote=Flamesnation]Derivative of cos is -sin..[/quote]
Oh, for some reason I anti-differentiated that. o.e
Thanks, man.

Reply January 21, 2014

LeadIn

[quote=Flamesnation]Derivative of cos is -sin..[/quote]

This, substitute u=cos7t
then ta-da, the thing that I hate the most about u-substitution is that once you sub one thing wrong you have to restart

Edit: from my understanding you should always substitute the "[b]u[/b]gly number" (i.e. (x)^1/2, (x)^(cos(x)) etc.)

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3 Comments • Newest first