d = square root of (x2 - x1)^2 + (y2 - y1)^2
M[(x1 + x2) / 2, (y1 + y2) / 2]
A circle is the set of all points in a plane that are equidistant from a fixed point.
(x-h)^2 + (y-k)^2 = r^2
A parabola is the set of all points in a plane equidistant from a given point and a given line.
Focus/directrix eqaution for parabola
a = (1/4p)
opens up/down: y - k = (1 / 4p)(x - h)^2
opens left/right: x - h = (1 / 4p)(x - h)^2
p = distance from vertex to focus
An ellipse is the set of all point in a plane such that the sum of the distance to two fixed points is a constant.
horizontal: [(x - h)^2 / a^2] + [(y - k)^2 / b^2] = 1
Vertical: [(x - h)^2 / b^2] + [(y - k)^2 / a^2] = 1
a^2 - b^2 = c^2
A hyperbola is the set of all points in a plane such that the difference to two fixed points is a constant.
left/right: [(x - h)^2 / a^2] - [(y - k)^2 / b^2] = 1
Up/down: [(y - k)^2 / a^2] - [(x - h)^2 / b^2] = 1
2 quadratics w/ same sign & same coefficient
2 quadratics w/ same sign & different coefficients
2 quadratics w/ different signs