““Exterior and Interior Exterior and Interior Angles of a TriangleAngles of a Triangle ““

Parts of TrianglesParts of TrianglesExterior angle - an Exterior angle - an

angle which forms a angle which forms a linear pair with an linear pair with an

angle of the triangle.angle of the triangle.

Remote interior angle – Remote interior angle – In the figure at the In the figure at the

right, angle ABD is an right, angle ABD is an exterior angle of exterior angle of

triangle ABC and angle triangle ABC and angle A and angle C are its A and angle C are its

remote interior angles.remote interior angles.

The Exterior Angle TheoremThe Exterior Angle Theorem(EAT)(EAT)

• The The measure of an measure of an exterior angle of a exterior angle of a triangletriangle is equal to the sum is equal to the sum of the of the measures of its two measures of its two remoteremote interior angles. interior angles.

For Example........For Example........

• #1#1What is the measure of the exterior angle in What is the measure of the exterior angle in

the figure?the figure?

Solution:Solution:

CorollaryCorollary

• The measures of an The measures of an exterior angle of a triangle exterior angle of a triangle is greater than the measure is greater than the measure of either of its remote of either of its remote interior angle.....interior angle.....

I guess that’s all you need to know………

THE THE

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Submitted by: Ket Wee Dy