EXTERIOR ANGLE THEOREM - South Hadley Public Schools · 72 no anim.notebook 3 Dec 156:26 PM 1 2 34...
Transcript of EXTERIOR ANGLE THEOREM - South Hadley Public Schools · 72 no anim.notebook 3 Dec 156:26 PM 1 2 34...
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Section 72
EXTERIORANGLE
THEOREM
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An exterior angle of a triangle is anangle that forms a linear pair with one of the interior angles of a triangle.
Exterior Angles
Each exterior angle has two remote interior angles associated with it. Remote interior angles of a triangle are the two interior angles that are away from an exterior angle.
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Example 1
a. Name the two remote interior angles of ΔPQR with respect to
b. Name the two remote interior angles of ΔPQR with respect to
c. Name the two remote interior angles of ΔPQR with respect to
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Use a straightedge to draw and label ΔRPN. Extend side through K to form theexterior angle 4.
1. Use a protractor to find 2. Use a protractor to find
3. Use a protractor to find 4. Find
Make a conjecture about how the measure of an exterior angle relates to the measures of its two remote interior angles.
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The Exterior Angle TheoremThe measure of an exterior angle is equal to thesum of the measures of its two remote interior angles.
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Example 2
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a. If and what is
b. What is if and
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c. If and find the value of x.
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d. If and find the value of x. Then find
Example 2 continued
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The measure of an exterior angleis greater than the measures ofeither of its two remote interiorangles.
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If a triangle has one right angle, then the other two angles must be acute.
Two More Theorems