The standard form of an equation of a circle centered at the x y r where r is the radius The hypotenuse of the triangle is a length is r Find the lengths of the legs The 1 PS y Substitute into the Pythagorean theorem y r where r is the Identifying the Radius and Center from an Equation h k 1 0 x 3 y 4 25 4 of the circle so its Q 0 0 and h k is the center of the circle form of an equation of a circle is x h y k r 2 x y 7 19 h is the value subtracted from x is the value Is T 19 h k 0 P x y S x 0 from