Solve the Problem $r$ And the Circumference $C = 2 \pi r$

question 354

Multiple Choice

Solve the problem.
-Suppose that the radius $r$ and the circumference $C = 2 \pi r$ of a circle are differentiable functions of $t .$ Write an equation that relates $\mathrm { dC } / \mathrm { dt }$ to $\mathrm { dr } / \mathrm { dt }$ .

• A) \(\frac { d C } { d t } = 2 \pi \frac { d r } { d t }\)
• B) \(\frac { d C } { d t } = 2 \pi r \frac { d r } { d t }\)
• C) \(\frac { d C } { d t } = \frac { d r } { d t }\)
• D) \(\frac { d r } { d t } = 2 \pi \frac { d C } { d t }\)

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