# Difference between revisions of "Sum of the interior angles of a quadrilateral"

The sum of the measures of the angles in any quadrilateral is 4 right angles.

### Objectives

To establish that sum of interior angles of any quadrilateral is 360°

40 minutes

### Prerequisites/Instructions, prior preparations, if any

Prior knowledge of point, lines, angles, intersecting lines, vertically opposite angles, properties of triangle

### Process (How to do the activity)

• In the geogebra sketch for the quadrilateral measure the sides and angles at the vertices
• Calculate the sum of these angles of the quadrilateral? Note your observations
 Quadrilateral Side1 Side2 Side3 Side4 Angle1 Angle2 Angle3 Angle4 Angle1+Angle 2+ Angle3 + Angle 4 Whatdo you observe about their sum Q1 Q2 Q3
• Draw any one diagonal. What do you notice? What is the quadrilateral divided into? How many triangles are formed?
• What is the measure of the sum of angles in each quadrilateral? So what is the measure of all the angles of the quadrilateral?
• Make different quadrilaterals. Divide it into two triangles, measure the angles of the two triangles, check their sum.
• Tabulate the angles of the two triangles
 Observation Triangle1 Triangle2 Sum of angles of two triangle Angle 1 Angle 2 Angle 3 Sum of angles Angle 1 Angle 2 Angle 3 Sum of angles Q1 Q2 Q3

Evaluation at the end of the activity

• Is the sum of all angles in any quadrilateral 360o.