Circle with Centre (0,0) (Leaving Cert Mathematics): Quizzes

Points at fixed distance from centre

$x^2 + y^2 = r^2$

Radius of the circle

Diameter is $2r$

$C = 2\pi r$

$A = \pi r^2$

Substitute into equation; if true, on circle

$r = 7$

Yes, it lies on the circle

Coordinates of any point on circle