Download Geometry SOL Notes Topic #3 – Angles (general) Classification

Geometry SOL Notes
Topic #3 – Angles (general)
Angles are measured as a fractional amount of a full circle = 360°.
Classification
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Acute – measures between 0° and 90°
Right – measures exactly 90°
Obtuse – measures between 90° and 180°
Straight – measures exactly 180°
Terms
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Complementary – two angles whose sum is 90°
Supplementary – two angles whose sum is 180°
Angles form by Intersecting Lines
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Vertical angles – across from each other – are congruent
 1  3, 2  4
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Linear
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pairs – two angles forming a straight line – are supplementary
m1  m2  180
m2  m3  180
m3  m4  180
m4  m1  180
4
1
3
2
1
Triangles
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The sum of the interior angles of a triangle is 180°.
 m1  m2  m3  180
The exterior angle equals the sum of the nonadjacent interior angles.
 m4  m1  m2
Isosceles triangles – base angles are equal
 5  6
Equilateral triangles – all angles are equal
 7  8  9
5
7
9
8
2
3
6
4