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Sum of angles in a triangle (Theorem) |
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The sum of the measures of the interior angles of a triangle is 180 |
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a line that is added to a diagram to help in a proof |
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Draw a line through a point parallel to another line (Reason) |
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Through a point outside a line, there is exactly one line through the point that is parallel to the given line. |
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a statement that can be proven easily from a theorem |
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Third angle is congruent since 2 angles are congruent (Corollary) |
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If angles of one triangle are congruent to two angles of a second triangle, then the third angle is also congruent. |
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Angle in equiangular triangle = 60 (Corollary) |
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Each angle of an equiangular triangle is 60. |
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# of right or obtuse angles possible in a triangle (Corollary) |
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In a triangle, there can be at most one right angle or one obtuse angle. |
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Acute angles of a right triangle (Corollary) |
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The acute angles of a right angle are complementary. |
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Measure of an exterior angle (Corollary) |
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The sum of the measures of the 2 remote angles is the same as the measure of the exterior angle. |
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a figure formed by three segments joining three noncollinear points |
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Points of a figure; intersection of two noncollinear segments |
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At least 2 sides congruent |
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all angles congruent, angle=60 |
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1) Formed by sides 2) Each segment intersects exactly two other segments, one at each endpoint 3) No two segments with common endpoint are collinear |
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polygon such that no line containing a side of the polygon contains a point in the interior of the polygon |
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a segment joining two nonconsecutive vertices in a polygon |
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The sum of the measures of a polygon (Theorem) |
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The sum of the measures of the angles of a convex polygon with n sides is 180(n-2) |
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Sum of exterior angles (Theorem) |
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The sum of the measures of the exterior angles of any convex polygon, one angle at each vertex, is 360. |
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A polygon that is both equiangular and equilateral |
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Practice Problem: How many sides are in a regular polygon whose interior angle is 165. |
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24 sides 180-165=15, 360/15=24 |
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