You can put this solution on YOUR website!
Lets use a rough sketch to define this situation.
draw a circle. Then draw a radius in the horizontal to right position.
If we then draw a chord, perpendicular to the radius, about 2/3 way out on radius.
Now finally draw a line from the center of the circle, to where the chord intercects the circle.
This last line is a radius, pls label "r". It is also the hypotenuse to a right triangle, formed by the initial horizontal radius, and the perpendicular chord.
This right triangle can be understood using the pythagorean theorem, c^2 = a^2 +b^2.
Generally, this is all that is required.
Please remember also that the total chord is bisected into two equal lengths by the
Hopefully this helps your ubderstanding.