Find the coordinates of the centre radius of each of the following circle:

Given: the equation of the circle is



x2 + y2 + 2xcosθ + 2ysinθ - 8 = 0 ..... (1)


We know that for a circle


x2 + y2 + 2ax + 2by + c = 0 .... (2)


Centre = (- a, - b)


Radius =


Comparing (1) with (2) we get,


Centre =


Centre = (- cosθ, - sinθ)


Radius =


Radius =


Radius =


Radius = √9


Radius = 3


The centre and radius of the circle is (- cosθ, - sinθ) and 3.


1