Page 23 - TB_5B

Activity 1 The Sum of the Angles in a Triangle

Learn how to find the sum of the angles in a triangle.

Method 1 Use a protractor. What you need: Protractor

a d g
bc ef hi

ABC
abcde f gh i
Angle ( )

Sum of the
Interior Angles ( )

Method 2 Cut out the angles in a triangle.

Cut out the angles in Put the angles Use a protractor to
a triangle. together as shown find the sum of the
below. three angles.

Find the sum of the three angles. The sum of the angles in
+ + = 180Ø a triangle can be found by
drawing two parallel lines
Therefore, the sum of the angles in a triangle is and using the property of
180Ø.
the alternate angles.

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