Equation of a Circle (Leaving Cert Mathematics): Flashcards

Set of points at fixed distance (radius) from fixed point (centre)

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

$(x-h)^2 + (y-k)^2 = r^2$

$x^2 + y^2 + 2gx + 2fy + c = 0$

$(-g, -f)$

$r = sqrt{g^2 + f^2 - c}$

$h$ (the $x$-coordinate of centre)

$k$ (the $y$-coordinate of centre)

Substitute its coordinates into the circle's equation

Complete the square for $x$ and $y$ terms

Tangents, chords, intersections with lines

$(3, -4)$