Parallelogram
A quadrilateral with two pairs of parallel sides
Lel
If parallelogram, then…
If ____________, then parallelogram.
If rectangle, then…
If ____________, then rectangle.
- diagonals are congruent and bisect each other
If rhombus, then…
If ____________, then rhombus.
Polygon Angle Sum Theorem
The sum of the interior angles of a convex polygon with (n) sides is 180(n-2) degrees.
Polygon Exterior Angle Sum Theorem
The sum of the exterior angle measures of a convex polygon is 360 degrees.
If square, then…
If kite, then…
If isosceles trapezoid, then…
If trapezoid and ____________, then isosceles trapezoid.
Trapezoid Midsegment Theorem
The length of the midsegment of a trapezoid is half the sum of the base’s lengths.
Perimeters of Similar Polygons
If two polygons are similar, then their perimeters are proportional to the scale factor between them.
SSS Similarity
If the corresponding side lengths of two triangles are proportional, then the triangles are similar.
SAS Similarity
If the lengths of two sides of one triangle are proportional to the lengths of two corresponding sides of another triangle and the included angles are congruent, then the triangles are similar.
Triangle Proportionality Theorem
If a line is parallel to one side of a triangle and intersects the other two sides, then it divides the sides into segments of proportional lengths.
Converse of Triangle Proportionality Theorem
If a line intersects two sides of a triangle and separates the sides into proportional corresponding segments, then the line is parallel to the third side of the triangle.
Triangle Midsegment Theorem
A midsegment of a triangle is parallel to one side of the triangle, and its length is one half of the length of that side.
If similar triangles, then…
-lengths of corresponding altitudes, angle bisectors, and medians are proportional to lengths of corresponding sides
Triangle Angle Bisector
Separates the opposite side into two segments that are proportional to the lengths of the other two sides.
Congruent Arcs
In the same or congruent circles, two minor arcs are congruent if and only if their central angles/corresponding chords are congruent.
If the radius or diameter of a circle is perpendicular to a chord…
…then it bisects the chord and arc.