HYPERBOLA
A hyperbola is a curve where the distances of any point from:
- a fixed point (the focus), and
- a fixed straight line (the directrix) are always in the same ratio.
This ratio is called the eccentricity, and for a hyperbola it is always greater than 1.
The hyperbola is an open curve (has no ends).
But that isn't the full story! Because a hyperbola is actually two separate curves in mirror image like this:
- a directrix and a focus (one on each side)
- an axis of symmetry (that goes through each focus, at right angles to the directrix)
- two vertices (where each curve makes its sharpest turn)
And, strictly speaking, there is also another axis of symmetry that reflects the two separate curves of the hyperbola.
| Conic Section You can also get a hyperbola when you slice through a cone. The slice must be steeper than that for a parabola, but does not have to be parallel to the cone's axis for the hyperbola to be symmetrical. So the hyperbola is a conic section (a section of a cone). |
By placing a hyperbola on an x-y graph (centered over the x-axis and y-axis), the equation of the curve is:
x2/a2 − y2/b2 = 1
| Also: One vertex is at (a, 0), and the other is at (−a, 0) The asymptotes are the straight lines:
|
Eccentricity
We already mentioned the eccentricity (usually shown as the letter e), it shows how "uncurvy" (varying from being a circle) the hyperbola is.
- P is a point on the curve,
- F is the focus and
- N is the point on the directrix so that PN is perpendicular to the directrix.
It can also given by the formula:
| e = |
Latus Rectum
| The Latus Rectum is the line through the focus and parallel to the directrix. The length of the Latus Rectum is 2b2/a. |
REFERENCES
http://www.mathsisfun.com/geometry/hyperbola.html