Question

answer the pic please

Answer 1

For a right angle triangle, radius of circumcircle is half of hypotenuse.
$hypotenuse = \sqrt{ {20}^{2} + {21}^{2} } = 29 \: cm \\ therefore \\ radius \: \: of \: \: circumcircle \\ = \frac{29}{2} = 14.5 \: cm$