Question

a circle has a center at (3,5) the point (3,8) is on the circle what is the circumference of the circle to the nearest tenth of a unit?

Answer 1

You need to use the distance formula to find the radius of the circle.

$d = \sqrt{(x_2 - x_1)^2 + (y_2-y_1)^2} \\ \\ d = \sqrt{(3-3)^2 + (8-5)^2} \\ \\ d = \sqrt{0^2+3^2} \\ \\ d = \sqrt{9} = 3$

The radius is 3.

The circumference is $2 \pi r$

$= 6\pi \\ \\ =18.8$