The Parabola is defined as the locus of a point which moves so that it is always the same distance from a fixed point (called the focus) and a given line (called the directrix).

Using the distance formula,

, squaring both sides makes

Simplifying gives us the formula for a parabola:

which can also be written as

If the axis of a parabola is horizontal then the equations becomes

 

 

Please continue to lesson 2