Question

Find the equation of the circle with centre (2, −1) and passing through the point (3, 6) in standard form

Answer 1

Centre = C = (2, −1)

Passing through = A = (3, 6)

So radius = CA

= `sqrt((2 - 3)^2 + (- 1 - 6)^2)`

= `sqrt(1 + 49)`

= `5sqrt(50)`

Now centre = (2, −1) and radius = `sqrt(50)`

So equation of the circle is

(i.e) (x – 2)² + (y + 1)² = `sqrt(50)^2`

⇒ (x – 2)² + (y + 1)² = 50