Geometry Flashcards
Vertex of an angle
The point of intersection
Parallel
Two lines are parallel if they lie in the same plane and never intersect each other
Acute angle
Angle whose degree measure is between 0 and 90 degrees
Right angle
Is exactly 90 degrees
Obtuse angle
Angle whose degree measure is between 90 and 180
Straight angle
Exactly 180 degrees
Perpendicular
Two lines are perpendicular if they intersect at a 90 degree angle.
Supplementary angles
Two angles are supplementary if the sum of their measures is 180
Complementary
Two angles are complementary if the sum of their measures is 90
Bisect an angle
A line or line segment bisects an angle if it splits the angle into two smaller, equal angles
Vertical angles
Pair of opposite angles formed by two intersecting line segments.
At the point of intersection two pairs of vertical angles are formed.
The two angles in a pair have the same degree measure.
Exterior Angle Theorem
The exterior angle of a triangle is equal to the sum of the two remote (nonadjacent) interior angles of the triangle.
What to do with a 75-60-45 triangle
Split into two right triangles by splitting the 75 degree angle. This will create one 45-45-90 triangle and one 30-60-90 triangle.
Are two triangles congruent?
If one of the following applies:
- the three sides are all congruent to the other triangle
- if two sides and the included angle are congruent to another
- if two angles and the included side are congruent to the other.
Tangent lines
If a line is tangent to a circle (intersects it at exactly one point), then a radius drawn from the center of the circle to the point of tangency is perpendicular to the line.
