Posted by Erica on .
F(x) = cos(x) • the integral from 2 to x² + 1 of
e^(u² +5)du
Find F'(x).
When i did this, i got:
2xsin(x)e^((x²+1)² + 5)
But my teacher got:
sin(x) • the integral from x² + 1 of e^(u² +5)du + 2xcos(x)e^((x²+1)² + 5)
Do you know why the integral is in his answer? I'm not sure where I went wrong. If you could help, I would greatly appreciate it. Thanks!!

Calculus 
Steve,
Leibnitz's Rule explains how to take the derivative of an integral. Take a google for it, or consult your textbook.
Basically, you have a product here. cos(x) * Integral f(x)
d/dx of the product is
sin(x) * Integral + cos(x) * d/dx(Integral(f))
d/dx(Integral) = Integral(df/dx) = f, evaluated at the limits of integration.