Using this data. Create a Triangle with the Chord and Center of the dot. We know the distance between the chord and center which is one length of one of the sides.
We split the chord from the intersecting line from the center to the chord making the second line being 7.5cm
After We draw a line from the center of the circle to where the chord meets to the edge of the circle to create the triangle
We now have 2 measurements and can use Pythagorean Theorem to determine the radius from the missing length of the triangle.
