Answer:
Part 12)

Part 13)

Explanation:
Part 12) we know that
The equation of a circle in center-radius form is equal to

where
(h,k) is the center of the circle
r is the radius of the circle
In this problem
Looking at the graph
The center is the

The radius is

substitute in the expression above


Part 13) we know that
The measure of the external angle is the semi-difference of the arcs it covers.
so
![m\angle ABC=(1)/(2)[arc\ DE-arc\ AC]](https://img.qammunity.org/2021/formulas/mathematics/high-school/8uqsuhnvm5vpprpoulwpt2u7iw1t70bwd6.png)
we have


![m\angle ABC=(1)/(2)[142^o-48^o]](https://img.qammunity.org/2021/formulas/mathematics/high-school/ellxs63bmkww0wtuih78xoxwdkt0w1pl98.png)
