directrix - line in a parabola not through the focus
Free Parabolas Calculator - Determines the focus, directrix, and other related items for a parabola.
Free Polar Conics Calculator - Given eccentricity (e), directrix (d), and angle θ, this determines the vertical and horizontal directrix polar equations.
An Automated Online Math Tutor serving 8.1 million parents and students in 235 countries and territories.
