A circle has a radius that increases at a rate of 10cm/s. Find the eaaquation of the outermost circle 6 seconds after it starts to expand.

Answer 1

Equation for what, the circumference?

C=2PI r
dC/dt=2PI dr/dt

For area:
Area=PI r^2
dA/dt=2PI r dr/dt

but r=10+6t
dA/dt=2pi(10+36)10

Answer 2

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