# Trig derivative

1. Oct 31, 2009

### temaire

1. The problem statement, all variables and given/known data

Find the first derivative of the function $$y=cos[(8t-7)^{\frac{-6}{7}}]$$

3. The attempt at a solution
$$\frac{dy}{dx}=\frac{48sin[(8t-7)^{\frac{-6}{7}}]}{7(8t-7)^{\frac{13}{7}}}$$

How can I simplify this further?

2. Oct 31, 2009

### Dick

You can't simplify it in any significant way. Just leave it as it is.

3. Oct 31, 2009

### temaire

Well the thing is, I'm using a program called MathXL, and when I try to submit this answer, it rejects it.

4. Oct 31, 2009

### temaire

So you think the program is just malfunctioning? I doubt this because a friend of mine had the same problem as well.

5. Nov 1, 2009

6. Nov 1, 2009

### temaire

The answer is correct, but it looks like they wanted all the exponents to be positive. I put this in, and got it right.

$$\frac{dy}{dx}=\frac{48sin[\frac{1}{(8t-7)^{\frac{6}{7}}}]}{7(8t-7)^{\frac{13}{7}}}$$

7. Nov 1, 2009

### Dick

Good job. Shows you the limitations of the program. I really wish good answers weren't subjected to this hoop jumping.