00:03
All right, because this has an e in it, i need to think about what i know how to integrate that has e in it.
00:09
And the only thing i know is e to the u, d, u, and its integral is e to the u plus c.
00:15
So that doesn't give me very much choice here.
00:17
I'm going to have to let you be the cosine of x.
00:22
Then du is the derivative of the cosine, which is minus the sine of x, d x.
00:28
Oh, it's not terrible.
00:30
Because look, there's the sign of x right there.
00:32
There's sine x, dx.
00:33
If only had a minus sign, i would be done.
00:36
Almost done.
00:37
So i'll just put one in there.
00:39
And you can't go around just put minus signs in things unless you take care of it by doing the opposite.
00:46
Or in this case, the same thing.
00:47
Because when you multiply two negative ones, you get positive one...