Chord of Contact from an External Point

Chord of Contact from an External Point

For:

$$\frac{x^2}{a^2}+\frac{y^2}{b^2}=1$$

the chord of contact from the point $$P(x_1,y_1)$$ is:

$$\frac{xx_1}{a^2}+\frac{yy_1}{b^2}=1$$

Usage

- Used to find the line joining the two points of contact of tangents drawn from an external point.