Unit D Flashcards
Theorem 4-1
If 2 corresponding angles of a triangle are congruent, then the third angles are congruent
Congruent Polygons
- congruent corresponding sides and angles
- list in corresponding order
Triangle
- formed by 3 non-collinear points connected by segments
- each pair of segments of a triangle form an angle
- vertex of each angle is a vertex of the triangle
- named by vertices
Equiangular Triangle
- all angles are congruent
Acute Triangle
- all angles are between 0º and 90º
Right Triangle
- 1 angle must be 90º
Obtuse Triangle
- 1 angle is between 90º and 180º
Equilateral Triangle
- all sides are congruent
Isosceles Triangle
- 2 sides are congruent (legs)
Scalene Triangle
- no sides are congruent
Triangle Angle-Sum Theorem
The sum of the measures of a triangle add up to 180º
Triangle Exterior Angle Theorem
The measure of the exterior angle is equal to the sum of the 2 remote interior angles
Isosceles Triangle Theorem
If the 2 legs are congruent, then the base angles are congruent
Converse of Isosceles Triangle Theorem
If the base angles are congruent, then the sides are congruent
Vertex Angle Bisector Theorem
The bisector of the vertex angle of an isosceles triangle is the perpendicular bisector of the base
Corollary to Theorem 4-4
If the triangle is equilateral, then it is equiangular
Corollary to Theorem 4-5
If the triangle is equiangular, then it is equilateral
SSS
If 3 sides of 1 triangle are congruent to the corresponding sides of another triangle, then the triangles are congruent.
SAS
If 2 sides and 1 included angle of 1 triangle are congruent to the corresponding included angle and sides of another triangle, then the triangles are congruent.
ASA
If 2 angles and 1 included side of 1 triangle are congruent to the corresponding angles and included side of another triangle, then the triangles are congruent.
AAS
If 2 angles and 1 non-included side of 1 triangle are congruent to the corresponding angles and non-included side of another triangle, then the triangles are congruent.
HL
If the hypotenuse and a leg of 1 right triangle are congruent to the hypotenuse and leg of another right triangle, then the triangles are congruent.
CPCTC
Corresponding parts of congruent triangles are congruent
Concurrent
When 3 or more lines intersect in 1 point
Point of Concurrency
Point at which 3 lines intersect
Perpendicular Bisector Theorem
The perpendicular bisector of the sides of the triangle are concurrent at a point equidistant from the vertices
Circumcenter
The point of concurrency of the perpendicular bisector of a triangle
Circumscribed
The circle about the triangle
Angle Bisector Theorem
The bisectors of the angles in a triangle are equidistance from the sides
Incenter
The point of concurrency of the angle bisectors of a triangle
Inscribed
The circle in a triangle
Median
A segment whose endpoints are a vertex and midpoint of the opposite side
Median Theorem
The medians of a triangle are concurrent at a point that is 2/3 the distance from each vertex to midpoint of the opposite side
Centroid
The point of concurrency of the medians
Altitude
The perpendicular segment from the vertex to the line containing the opposite side
Orthocenter
Where the lines that contain the altitudes of a triangle are congruent
Altitude Theorem
The lines that contain the altitudes are concurrent
Midsegments
A segment that connects the midpoints of 2 sides
Triangle Midsegment Theorem
If a segment joins the 2 sides of a triangle, then the segment is parallel to the third side and is half its length
Largest Angle and Side Theorem
If 2 sides of a triangle are not congruent, then the largest angle lies opposite the longest side
- scalene not isosceles
Largest Side and Angle Theorem
If 2 angles of a triangle are not congruent, then the largest side lies opposite the largest angle
- scalene not isosceles
Triangle Inequality Theorem
The sum of 2 sides of a triangle is greater than the measure of the 3rd side
Perpendicular Bisector Theorem
If a point is on the perpendicular bisector of a segment, then it is equidistance from the endpoints of the segments
Converse of Perpendicular Bisector Theorem
If a point is equidistance from the endpoints of a line segment, then the point is on a perpendicular bisector of a segment