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?

5
12
13

Answer 1

You want the distance from that point to the origin. Do you know how to find the distance between two points?

Answer 2

Simply use the triangle formula for perpendicular triangles, which says:
\[c^2 = a^2 + b^2\]
Where c is hyphotenus, a and b are sides.

In here
\[r^2 = 12^2 + 5^2 = 169\]
\[r = \sqrt{169} = 13\]

Answer 3

well a simple method is to know the standard form of the equation of the circle

\[(x - h)^2 + (y - k)^2 = r^2\]

(h, k) is the centre...

so substitute the given values

then substitute the point

this will allow you to calculate r^2

and then r... the radius... hope it helps

Answer 4

thank you:)