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## Homework Statement

Find the derivative of:

[itex]1. f(x)=arccos(5x^3)[/itex]

[itex]2. f(x)=∫cos(5x)sin(5t)dt[/itex] when the integral is from 0 to x

## Homework Equations

Chain rule, dy/dx=dy/du*du/dx

## The Attempt at a Solution

For the first one, I can just take 5x^3 as u and then apply the chain rule to get

[itex]-15x^2/\sqrt{1-5x^3}[/itex]

but maple TA keeps telling me that it's incorrect...

As for the second one, I'm not sure how to approach something like that when x is actually in the integral, as in the cos(5x). I mean, when I'm applying the chain rule...do I have to include cos in my choice of u?