(5x)Σcos(x) cosu^4 du=

I got 5cos(20x^3)+cos(4cos(x)^3)(sin(x)) but it is incorrect. can someone explain to me why this is incorrect help me correct it?

Printable View

- Nov 21st 2013, 04:41 PMrhcprule3FTC part 2 help
(5x)Σcos(x) cosu^4 du=

I got 5cos(20x^3)+cos(4cos(x)^3)(sin(x)) but it is incorrect. can someone explain to me why this is incorrect help me correct it? - Nov 22nd 2013, 02:34 PMchiroRe: FTC part 2 help
Hey rhcprule3.

What does the sigma refer to? Is it a summation and if so, what are the limits and dummy indices? - Nov 22nd 2013, 03:32 PMHallsofIvyRe: FTC part 2 help
With that "du" I'm inclined to believe you mean an integration with respect to u But then what about the "5x" and "cos(x)"? Do you mean, the simplest way I can interpret this,

$\displaystyle 5x cos(x) \int cos^4(u) du$? To integrate that you could use $\displaystyle cos^2(u)= (1/2)(1+ cos(2u))$, twice. But I cannot imagine where you could have got that "20" inside the cosine, much less the cube! So perhaps I am misunderstanding completely.