# Homework Help: Please check work on derivatives lab

1. Feb 25, 2010

### tjohn101

1. The problem statement, all variables and given/known data
Sorry about not using the template, but I didn't really see how I could have. If you guys/gals could please check over my answers to these questions and point out the ones I miss that would be outstanding. Thank you!!

1. The position of an object moving on a coordinate line is given by s=t2 −7t+10, were s is in meters
and t is in seconds. When, if ever, during the interval 0≤ t ≤7 does the object change directions?
Answer: at t = 3.5 sec

2. At time t, the position of an object moving along the s axis is s=t3−15t2+78t were s is in meters
and t is in seconds. Find the total distance traveled by the object from t = 0 to t = 3 .

3. Suppose that the cost of producing x radios is given by C(x)=800+40x−0.2x2 . Find the cost per radio of producing the first 30 radios.

4. Find the line tangent to the graph of f (x) =cosx at x = pi/2 .

5. Find the 34th derivative of f (x) = cosx.

6. g(x)=(cscx+cotx)(cscx−cotx) , find g'(x) .

7. f (x)= sqrt(11x−x5) , find f '(x) .

8. g(x)=sec5(x2−2x), find g'(x) .

9. Find the equation of the line tangent to the graph of f(x) = x3 x3+3 at x =1.

10. The total revenue from the sale of x stereos is given by
R(x) = 2000(1 - x/600)2. Find the marginal
revenue, if necessary round to the nearest thousandth.
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Feb 25, 2010

### mmmboh

I didn't check all of them, 1 is right, 2 I believe is right, I think 4 is -1, 5 is right, 7 is wrong, the answer should be $$\frac{11-5x^4}{2\sqrt[2]{(11x-x^5)}}$$.

You should use http://www.wolframalpha.com/" [Broken] to check your answers, just type in dervive "your equation" and it will show you the answer and steps.

Last edited by a moderator: May 4, 2017