Grade 11 → Coordinate Geometry ↓
Conic Sections
Conic sections are the curves obtained by cutting a double cone from a plane. These curves include circles, ellipses, parabolas, and hyperbolas. In coordinate geometry, conic sections are studied by examining their equations and graphs. Let us look at each type of conic section in detail.
Circle
A circle is a set of points on a plane that are equidistant from a fixed point called the center. The constant distance from the center to any point on the circle is called the radius.
The equation of a circle with centre ( (h, k) ) and radius ( r ) is:
(x - h)^2 + (y - k)^2 = r^2
When the center of the circle is at the origin ( (0, 0) ), the equation simplifies to:
x^2 + y^2 = r^2
Ellipse
An ellipse is a set of points where the sum of the distances from two fixed points (called foci) is constant. The major axis is the longest diameter of the ellipse, and the minor axis is the shortest.
The standard form of an ellipse with centre at ( (h, k) ) with principal axis along the x-axis is:
(frac{(x - h)^2}{a^2} + frac{(y - k)^2}{b^2} = 1)
Where ( a ) is the semi-major axis and ( b ) is the semi-minor axis. If ( a > b ), then the major axis is horizontal. If ( b > a ), then it is vertical.
Parabola
A parabola is a set of points such that any point on the parabola is equidistant from a fixed point called the focus and a fixed line called the directrix.
The standard form of a parabola with vertex at ( (h, k) ) can vary depending on its orientation:
- Vertical axis: ( y = a(x - h)^2 + k )
- Horizontal axis: ( x = a(y - k)^2 + h )
Hyperbola
A hyperbola is a set of points where the difference in distance from two fixed points (called foci) is constant. It has two branches, each pointing away from the center.
The standard form of a hyperbola with center at ( (h, k) ) and transverse axis along the x-axis is:
(frac{(x - h)^2}{a^2} - frac{(y - k)^2}{b^2} = 1)
If the transverse axis is along the y-axis, then the equation is:
(frac{(y - k)^2}{a^2} - frac{(x - h)^2}{b^2} = 1)
Properties of conic section
Each type of conic section exhibits the following distinctive features:
- Circle: no focus, constant radius.
- Ellipse: two focuses, centered at the midpoint of the major axis, affine distance sum constant.
- Parabola: Single focus and directrix, equally spaced vertices.
- Hyperbola: Two divergent branches, two focuses, constant difference of distances.
Applications of conic section
Conic sections have diverse applications in fields such as engineering, physics, astronomy, and architecture. For example:
- Elliptical: The orbits of the planets are elliptical, governed by Kepler's laws.
- Parabola: Parabolic mirrors and antennas focus waves to a point.
- Radio navigation and determination of locations are carried out using the hyperbolic theory.
Summary
Conic sections are an essential part of coordinate geometry. Each cone has unique properties and can serve practical purposes in real-life situations. Understanding the equations and characteristics of these curves increases knowledge about their geometric nature and applications.