One of the most basic geometric figure is a point. All other geometric
A line is the path describe by a moving point. A straight line segment is formed when we use a ruler to join two points, say A and B. We call the line segment AB or BA. A and B are called the end-points.
The diagram below shows part of lines with only one end-point and extending in only one direction. We call them rays.
A line is either straight or curved. The diagram shows a curved line. A curved line is also called a curve.
A plane is a flat surface in which any two points are joined by a straight line lying entirely on the surface. For example, the ceiling of a room is a horizontal plane while the wall of the room is a vertical plane.
Examples of planes
When two rays OA and OB meet at point O, an angle is formed. O is also known as the vertex of the angle and OA and OB are the sides or arms of the angles.
( drawn with geometer's sketchpad, u can download the trial version at www.keypress.com/sketchpad )
There are many different kinds of angles. Here are a few basic ones:
An Acute angle is less than 90 degrees.
(angle B is an acute angle)
A right angle is equal o 90 degrees.
An obtuse angle is larger than 90 degrees but less than 180 degrees.
(Angle B is an obtuse angle )
A straight angle is equal to 180 degrees.
Other kinds of angles include :
Reflex angles, which are larger than 180 degrees but less than 360 degrees, complementary angles, supplementary angles etc.