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SAI International School
CLASS - IX

Mathematics
Lesson Notes-4
Chapter-7: Triangles

Sub-Topic: Inequalities in a Triangle

Exterior Angle Property:

In a triangle an exterior angle is always greater than its interior
opposite angles.

We know that in a triangle, if two sides are equal then their opposite angles
are equal and conversely also true.

Similarly, in a triangle if two sides are not equal then their opposite side are
also unequal.

Let us see how they are unequal through theorems 7.6 and 7.7.

Theorem 7.6