# Thread: Need Immediate help, stuck on 2 calc problems

1. ## Need Immediate help, stuck on 2 calc problems

1. find dr/d (theta)
r=4-theta^2sin(theta)

and

2.Let x and y be differentiable functions of t, and let s=sqrt(5x^2+y^2) be functions of x and y.

a. How is ds/dt related if y is constant
ds/dt=?dx/dt

b. how is ds/dt related to dx/dt and dy/dt if neither x nor y is constant
ds/dt= ? dx/dt+?dy/dt

c.How is dx/dt related to dy/dt if s is constant
dx/dt=?dy/dt.

HAVE NO IDEA AND NEED HELP, PLEASE AND THANK YOU

2. ## Re: Need Immediate help, stuck on 2 calc problems

Originally Posted by Elonzos
1. find dr/d (theta)
r=4-theta^2sin(theta)

and

2.Let x and y be differentiable functions of t, and let s=sqrt(5x^2+y^2) be functions of x and y.

a. How is ds/dt related if y is constant
ds/dt=?dx/dt

b. how is ds/dt related to dx/dt and dy/dt if neither x nor y is constant
ds/dt= ? dx/dt+?dy/dt

c.How is dx/dt related to dy/dt if s is constant
dx/dt=?dy/dt.

HAVE NO IDEA AND NEED HELP, PLEASE AND THANK YOU
1. \displaystyle \begin{align*} r = 4 - \theta ^2 \sin{\theta} \end{align*}

This is a product of functions, so to differentiate you need to use the product rule.

2. a) Use implicit differentiation.

b) Use implicit differentiation.

c) If s is constant, its derivative is 0. But you will already have ds/dt from part b), so this will equal 0. You can then see how dx/dt and dy/dt are related.

3. ## Re: Need Immediate help, stuck on 2 calc problems

Thank you but I keep getting a red mark (wrong) when I do it so I'm not sure of the actual values. I worked them out several times. I think I need step by step solution

4. ## Re: Need Immediate help, stuck on 2 calc problems

You get a "red mark" so you are submitting these for credit?

5. ## Re: Need Immediate help, stuck on 2 calc problems

No, these are practice but they suppose to be real similar to the actual test. The test is tomorrow and it's timed. 60mins So I'm trying to learn it now.

6. ## Re: Need Immediate help, stuck on 2 calc problems

Originally Posted by Elonzos
Thank you but I keep getting a red mark (wrong) when I do it so I'm not sure of the actual values. I worked them out several times. I think I need step by step solution
You won't get a step by step solution. If you post what you have done, then we can tell you where you have gone wrong.