November 19, 2015
1.3 Exterior Angles
So far we have
looked at angles
formed by parallel
lines cut by a
transversal and
within triangles.
Today we will
continue to look at
angle relationships
by examining angles
on the inside and
outside of a triangle.
November 19, 2015
Rename each of the angles . . .
<a
<c
<b
<a
<XYZ
<b
<YXZ
<c
<XZY
November 19, 2015
exterior angles angles that are formed by extending the side of a triangle
remote interior angles the two angles across the triangle from the exterior angle
November 19, 2015
Calculate the missing angle measure in
each figure and record them in the table.
November 19, 2015
a) After completing the table, look for a pattern in the relationship
between the m<BCD (the exterior angle) and the sum of the m<A and
m<B (the remote interior angles).
b) Write a conjecture about the relationship between an exterior angle
of a triangle and the two remote interior angles.
November 19, 2015
If m<1 = 530 and m<2 = 710, find m<4
If m<2 = 780 and m<4 = 1270, find m<1
November 19, 2015
In each of the figures below, use your conjecture about
exterior angles to solve for x.
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November 19, 2015
In the figure below, find x.
November 19, 2015
1.
2.
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