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→Activity No # 2. Angle sum property of a triangle
# Cut out 3 angles of a triangle and join 3 vertices next to each other.
# Cut out 3 angles of a triangle and join 3 vertices next to each other.
# Repeat for different triangles. What do you infer?
# Repeat for different triangles. What do you infer?
===Activity No # External angle property of a triangle===
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* Estimated Time: 40 minutes
* Materials/ Resources needed: Laptop, geogebra file, projector and a pointer.
* Prerequisites/Instructions, if any:
# The students should know a triangle and its basic elements.
# They should know interior and exterior angles of a triangle.
# They should know that sum of angles along a straight line is 180 degrees.
* Multimedia resources: Laptop
* Website interactives/ links/ Geogebra Applets:
* Process (How to do the activity):
# The teacher can move the 'explain slider' to show how the sum of opposite interior angles equals to external angle.
* Developmental Questions (What discussion questions):
# Identify the interior angles of this triangle.
# What are exterior angles ?
# Name the exterior angle from the figure.
# Name its two opposite interior angles.
# What is the measure of the marked exterior angle?
# What is the sum of two opposite interior angles?
# What can you infer ?
* Evaluation :
# Reason out as to why external angle is equal to sum of opposite interior angles of a triangle.
* Question Corner:
# Try to prove external angle theorem using linear pair concept and angle sum property of a triangle
==Concept #2 - Types of triangles==
==Concept #2 - Types of triangles==