Idon't understand how to do this what equation do i set up (y=mx+b)

Tiara buys the pizza shown below: a circular pizza is shown. the edge of one slice is marked ab. what does the curve ab represent?

What is the first step of an indirect proof of a number that is divisible by two

The general form of the quetion of a circle is ax^2+by^2+cx+dy+e=0 where a=b=0 if the circle has a radius of three units and the center lies on the y axis which set of values of a, b, c, d, and e might correspond to the circle