Question

A circle has its center at the origin, and (5, -12) is a point on the circle. How long is the radius of the circle?

Answer 1

the standard form of a circle with the centre at the origin is

\[x^2 + y^2 = r^2\]

so use the point you are given

x = 5 and y = -12

substitute them and solve for r.

it's pythagoras' theorem....

and remember -12 ^2 is a positive number

hope it helps