Question

find the circumference of the circle passing through -1,4and having it's centre at origin

Answer 1

As we know that the general equation of circle is x² + y² = K

As circle passes through (-1,4) it should satisfy this equation

(-1)² + (4)² = K

Therefore K = 17

So equation of this circle will be
x² + y² = 17

To find the radius of this circle Put x = 0

So it intersects y axis at distance √17 from origin.

So radius of this circle is √17

Now, Circumference of circle will be

Circumference of circle = 2 π r

Circumference of circle = 2 * 3.14 * √17

Circumference of circle = 6.28√17

Circumference of circle = 25.9062 units