Category: 02. Angles, Lines, and Polygons

Introduction In this lesson we are given the coordinates of points in a coordinate plane. Joining these points with line segments we get a polygonal figure. We are required to identify the polygon so formed.Example 1: Plot the following points (-5, 3) (3,3) (-5,-3) in the coordinate plane. Join the points with line segments and…

IntroductionExample 1: Name the following polygon based on its number of sides. Solution Step 1: Given polygon has ten sides. Step 2: So it is a Decagon.

Introduction The sum of angles of a triangle is 180°. In a triangle, we know there are three angles and three sides. In this lesson we solve for missing angle measure given two angle measures in a triangle.Example 1: Find the missing angle in the given triangle below. Sum of angles in a triangle is…

Introduction Triangles can be classified according to their sides or according to their angles. All of each side or angle may be of different or the same sizes; any two sides or angles may be of the same size. The types of triangles classified by their sides are the following. Equilateral triangle − A triangle with…

Introduction Let us consider the acute, the right and the obtuse angles as follows. If we close the third sides of these angles, acute, right and the obtuse triangles are formed. These triangles always have at least two acute triangles. The third angle decides the type of triangle. If the third angle is acute it…

Definitions Parallel lines − If two lines are equidistant from each other extending indefinitely in both directions, then they are said to be parallel to each other. Parallel lines do not intersect each other. Perpendicular lines − If two lines intersect each other at right angles, they are called perpendicular lines. Rules to identify parallel and perpendicular…

Definitions Point − A basic geometric entity. It that has no length, width or height. It is described only by its position. This is a point Q Straight line − A set of points that extend indefinitely in both directions. This is an example of line UT. A line is a continuous set of points that continues…

Introduction We measure angles in degrees. Angles can also be measured in other units like radians. One complete rotation around a point is 360 degrees or 2 pi radians. We use a little circle ° following the number to mean degrees. For example, 60° means 60 degrees. A full circle is 360°; half a circle…

Definition An angle is formed when two lines intersect in a point. The rays emerging from the common point called vertex are the arms of the angle. The magnitude of how big or small an angle is given by its measure in degrees or some other units Example 1: Measure the following angle using a protractor. Solution Step 1:…