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An angle measuring less than 90 degrees
Acute angle
An angle measuring exactly 90 degrees.
Right angle
An angle measuring greater than 90 degrees and less than 180 degrees.
Obtuse angle
An angle measuring exactly 180 degrees
Straight angle
Angles with equal measures
Congruent Angles
Point where two lines meet forming an angle
Vertex
Side in common
Ray
Two angles that share a vertex, share a ray, have no common interior points (don’t overlap).
Adjacent Angles
Opposite pair of angles (non-adjacent) formed when two lines intersect. They share a vertex. Vertical angles are always congruent.
Vertical Angles
Two angles whose measures sum to 90o
Complementary Angles
Two angles whose measures sum to 180
Supplementary Angles
Two adjacent angles formed by a ray (or line) and a straight angle. Linear pairs are supplementary.
Linear Pair
Tool used to measure the number of degrees in an angle
Protractor
All angles acute
Acute triangle
One right Angle
Right triangle
One obtuse angle
Obtuse triangle
All angle congruent
Equiangular Triangle
All sides congruent
Equilateral Triangle
At least two sides congruent
Isosceles Triangle
No sides congruent
Scalene Triangle
The sum of the measures of interior angles of a triangle is 180
Triangle Sum Theorem
The measure of an exterior angle of a triangle equals the sum of the measures of its two remote interior angles
Triangle Exterior Angle Theorem
Cut in half (creating two equal halves)
Bisect
The sum of any 2 sides of a triangle must be greater than the measure of the third side.
Triangle Inequality Theorem
A line that intersects two lines at two different points
Transversal
If a transversal intersects two parallel lines, then corresponding angles are congruent
Corresponding Angles Postulate
If a transversal intersects two parallel lines, then alternate interior (or exterior) angles are congruent
Alternate Interior (or Exterior) Angles Theorem
If a transversal intersects two parallel lines, then same-side interior (or exterior) angles are supplementary
Same-side Interior (or Exterior) Angles Theorem