Page 6 - CONIC SECTION - EBOOK._Neat
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Conic section
PARABOLA
TO FORM A PARABOLA ACCORDING TO ANCIENT GREEK DEFINITIONS, YOU
WOULD START WITH A LINE AND A POINT OFF TO ONE SIDE. THE LINE IS
CALLED THE "DIRECTRIX"; THE POINT IS CALLED THE "FOCUS".
THE PARABOLA IS THE CURVE FORMED FROM ALL THE POINTS (X, Y) THAT
ARE EQUIDISTANT FROM THE DIRECTRIX AND THE FOCUS.
THE LINE PERPENDICULAR TO THE DIRECTRIX AND PASSING THROUGH THE
FOCUS (THAT IS, THE LINE THAT SPLITS THE PARABOLA UP THE MIDDLE) IS
CALLED THE "AXIS OF SYMMETRY".
THE POINT ON THIS AXIS WHICH IS EXACTLY MIDWAY BETWEEN THE FOCUS
AND THE DIRECTRIX IS THE "VERTEX"; THE VERTEX IS THE POINT WHERE THE
PARABOLA CHANGES DIRECTION.
"regular", or vertical, parabola (in blue), "sideways", or horizontal, parabola (in
with the focus (in green) "inside" the blue), with the focus (in green) "inside"
parabola, the directrix (in purple) below the parabola, the directrix (in purple) to
the graph, the axis of symmetry (in red) the left of the graph, the axis of
passing through the focus and symmetry (in red) passing through the
perpendicular to the directrix, and the focus and perpendicular to the directrix,
vertex (in orange) on the graph and the vertex (in orange) on the graph
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