The Circumscribed Circle

In a right-angled triangle, the two legs (the sides forming the right angle) have lengths a = 9 cm and b = 12 cm. What is the radius R of the circumscribed circle?

A right-angled triangle has sides with lengths a = 5 cm, b = 12 cm, and a hypotenuse c = 13 cm. What is the radius $r$ of the inscribed circle (inradius)?