Question

3. Find the equation of circle whose centre is at (0, 0) and of radius 5 cm.

Answer 1

(x2+y2−12y+11=0)or(x2+y2+4y−21=0)

Solution :

Let the centre of the circle be C(0,k)

It is given that the circle passes through P(3,2)

Then ,|CP|2=52⇔f(0−3)2+(2−k)2=52

⇔(2−k)=±4⇔k=6ork=−2

∴ the centre of the circles is (0,6)or(0,−2)

Hence, the equation of the circle is

[(x−0)2+(y−6)2=52]or[(x−0)2+(y+2)2=52]