Perpendicular lines have negative-reciprocal slopes.
Circle
The equation of a circle centered at (h, k) and with radius r is
(x − h)^2 + (y − k)^2 = r^2
Parabola
The graph of the general quadratic equation y = ax^2 + bx + c is a
parabola with an axis of symmetry parallel to the y-axis.