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.