Confusion With Related Rates HW

[cnrrehab]

Homework Statement

The area A of a triangle with sides of lengths a and b enclosing an angle of measure $\theta$ is:

A=1/2 ab sin ($\theta$)

How is dA/dt related to d$\theta$/dt if side a and side b is constant?

Homework Equations

The Attempt at a Solution

I am pretty sure that I need to differentiate with respect to t. So since the 1/2, a and b are constant, would I just take the derivative of sin $\theta$, so it would look like:

dA/dt= 1/2 ab * cos $\theta$? I feel like I am missing something. If I am using the chain rule, would I add d$\theta$/dt at the end? I am a little confused. Thanks in advance for any help as I am taking Calculus over the summer, and it is not easy.

 

[tiny-tim]

welcome to pf!

hi cnrrehab! welcome to pf!

(have a theta: θ )

I am pretty sure that I need to differentiate with respect to t. So since the 1/2, a and b are constant, would I just take the derivative of sin $\theta$, so it would look like:

dA/dt= 1/2 ab * cos $\theta$? I feel like I am missing something. If I am using the chain rule, would I add d$\theta$/dt at the end?

that's right!

as you know, the https://www.physicsforums.com/library.php?do=view_item&itemid=353" says d(absinθ)/dt = d(absinθ)/dθ dθ/dt = abcosθ dθ/dt