Question

Find the centre and radius of the circle whose parametric equation is `x= -1+2 cos theta , y= 3+2 sin theta`.

Answer 1

We have `(x+1)/(2)=cos theta` and `(y-3)/(2)=sin theta`
Squaring and adding, we get
`((x+1)/(2))^(2)+((y-3)/(2))^(2)=1`
or `(x+1)^(2)+(y-3)^(2)=4`
Centre of the circle is `(-1,3)` and radius is 2.