Chapter 4, Problem 3CCSR

To determine

To find: Domain of the function $C=2\pi r$

Answer to Problem 3CCSR

Option C is correct

Explanation of Solution

Given information: The function $C=2\pi r$ gives the circumference C of a circle with radius r

Domain refers to all the input values that go into a function.

The radius $r$ can take the values $(0,\infty )$

So,

  $0<r<\infty$

Now find the values of the domain of the circumference.

Multiply both sides of $0<r<\infty$ by $2\pi$

  $\begin{array}{l}0\times 2\pi <r\times 2\pi <\infty \times 2\pi \\ 0<2\pi r<\infty \\ 0<C<\infty \end{array}$

So,

Domain is set of positive real numbers.

Option C is correct.