The center of a circle is at the origin. An endpoint of a diameter of the circle is at (-3 -4). How long is the diameter of the circle?

Find the distance between the point (-3, -4) and the origin to find the radius of the circle.

This is the distance formula:

d = ( ((x2 - x1)^2) + ((y2 - y1)^2) ) ^ 0.5

These are the points:

(x1, y1) = (0, 0)

(x2, y2) = (-3, -4)

d = ( ((-3 - 0)^2) + (-4 - 0)^2) ) ^ 0.5

d = ( (-3^2) + (-4^2) ) ^ 0.5

d = ( 9 + 16 ) ^ 0.5

d = ( 25 ) ^ 0.5

d = 5

Now that you know the radius of the circle, to find the diameter, just double it.

5 * 2 = 10

The diameter of the circle equals 10.