Grade 4 - Mathematics 2.1 1 and 2 Dimensional Figures
A flat surface is called a plane.
Infinite number of points can be marked on a plane.
A straight line that has no end points is called a line.
A straight line that has one end point is called a ray.
A straight line that has two end points is called a segment.
When two rays meet at a common point called the vertex, an angle is formed.
An angle that measures 90 degrees is called a right angle.
An angle that measures less than 90 degrees is called acute angle.
An angle that measures more than 90 degrees is called obtuse angle.
Two lines that cross through each other are called intersecting lines.
Two lines that form 90 degrees on intersection are called perpendicular lines.
Two lines that do not intersect each other at any point are called parallel lines.
A line segment that extends from the center of a circle to a point on the circle is called radius.
A line segment that has two of the end points on the circle is called the diameter.
Directions: Answer the following questions. Also draw a ray, line, segment, acute angle, obtuse angle, right angle, parallel lines, perpendicular lines, intersecting lines, circle with radius and diameter.