Lesson 4­3 Triangles.notebook
March 02, 2016
Lesson 4:3
Triangles and the
Exterior Angle
Theorem
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Lesson 4­3 Triangles.notebook
March 02, 2016
http://www.mathsisfun.com/proof180deg.html
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Lesson 4­3 Triangles.notebook
March 02, 2016
Triangles can be classified based on angle measurements and side measurements.
Angle Measurements:
• Acute: all three angles are less than 90
• Right: one right angle
• Obtuse: one obtuse angle
Side Measurements:
• Equilateral: all three sides are equal
• Isosceles: two equal sides (and two equal angles)
• Scalene: no equal sides
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Lesson 4­3 Triangles.notebook
March 02, 2016
Examples: Find the missing angle(s).
S
x
N
56o
1. 62o
U
131o
2. 4x
3x
x ­ 5
3. 2x
3x ­
1
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Lesson 4­3 Triangles.notebook
March 02, 2016
Exterior Angle Theorem
The 2 angles that are not adjacent, or next to, the exterior angle of the triangle are called remote interior angles
The measure of the exterior angle is equal to the sum of the measures of the two remote interior angles.
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Lesson 4­3 Triangles.notebook
4. March 02, 2016
33o
42o
x
2x + 1
5. 6. 24o
97o
85o
3x
163o
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Lesson 4­3 Triangles.notebook
March 02, 2016
Worksheet 4­3
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Lesson 4­3 Triangles.notebook
March 02, 2016
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