Theorems
Theorems
Terms
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- Theorem 9
- if two sides of a triangle are equal, the angles opposite them are equal
- Theorem 13
- if two sides of a triangle are unequal, the angles opposite them are unequal in the same order
- Theorem 27
- a quadrilateral is a parallelogram if its opposite sides are equal
- Theorem 57
- if a line through the center of a circle bisects a chord that is not a diameter, it is also perpendicular to the chord
- Theorem 5 (linear pairs)
- the angles in a linear pair are supplementary
- Theorem 21
- an exterior angle of a triangle is equal to the sum of the remote interior angles
- Theorem 40
- the area of a parallelogram is the product of any base and its corresponding altitude
- Theorem 8 (linear pairs/perpendicular)
- if the angles in a linear pair are equal, then then their sides are perpendicular
- SSS Similarity Theorem
- if the sides of one triangle are proportional to the sides of another triangle, then the triangles are similar
- Theorem 15 (triangle inequality)
- sum of any two sides of a triangle is greater than the third side
- SAS Similarity Theorem
- if an angle of one triangle is equal to an angle of another triangle and the sides including these angles are proportional, then the triangles are similar
- Theorem 31
- all rectangles are parallelograms
- Theorem 41
- the area of a trapezoid is half the product of its altitude and the sum of its bases
- Theorem 25
- the opposite sides and angles of a parallelogram are equal
- Theorem 28
- a quadrilateral is a parallelogram if its opposite angles are equal
- Theorem 29
- a quadrilateral is a parallelogram if two opposite sides are both parallel and equal
- Theorem 3 (complements)
- complements of the same angle are equal
- Theorem 7 (perpendicular lines)
- perpendicular lines form right angles
- Theorem 37 (midsegment)
- a midsegment of a triangle is parallel to the third side and half as long
- Theorem 56
- if a line through the center of a circle is perpendicular to a chord, it also bisects the chord
- Theorem 60
- if a line is perpendicular to a radius at its outer endpoint, it is tangent to the circle
- Theorem 20 (triangle angle sum)
- the sum of the angles of a triangle is 180 degrees
- Theorem 2 (B.O.R.)
-
if OA-OB-OC, then
- Theorem 51
- In a 30-60-90 triangle, the hypotenuse is twice the shorter leg and the longer leg is the square root of 3 times the shorter leg
- Theorem 6 (vertical angles)
- vertical angles are equal
- Theorem 24 (quadrilateral angle sum)
- the sum of the angles of a quadrilateral is 360 degrees
- Theorem 43 (converse of pythagorean)
- if the square of one side of a triangle is equal to the sum of the squares of the other two sides, the triangle is a right triangle
- Theorem 59
- if a line is tangent to a circle, it its perpendicular to the radius drawn to the point of contact
- Theorem 17
- equal corresponding angles mean that lines are parallel
- Theorem 16
- in a plane, two points each equidistant from the endpoints of a line segment determine the perpendicular bisector of the line segment
- Theorem 1 (B.O.P.)
- if A-B-C, then AB+BC=AC
- Theorem 14
- if two angles of a triangle are unequal, the sides opposite them are unequal in the same order
- Theorem 10
- if two angles of a triangle are equal, the sides opposite them are equal
- Theorem 26
- the diagonals of a parallelogram bisect each other
- Theorem 36
- the diagonals of an isosceles trapezoid are equal
- Theorem 53
- two nonvertical lines are perpendicular iff the product of their slopes is -1
- Theorem 12 (exterior angle)
- an exterior angle of a triangle is greater than either remote interior angle
- Theorem 42 (pythagorean)
- the square of the hypotenuse of a right triangle is equal to the sum of the squares of its legs
- Theorem 23 (hl)
- if the hypotenuse and a leg of one right triangle are equal to the corresponding parts of another right triangle, the triangles are congruent
- Theorem 32
- all rhombuses are parallelograms
- Theorem 46
- corresponding altitudes of similar triangles have the same ratio as that of the corresponding sides
- Theorem 19
- parallel lines form equal corresponding angles
- Theorem 49
- the altitude to the hypotenuse of the a right triangle forms two triangles similar to it and to each other
- Theorem 52
- two nonvertical lines are parallel iff their slopes are equal
- Theorem 18
- in a plane, two lines parallel to a third line are parallel to each other
- Theorem 11 (sss)
- if the three side of one triangle are equal to three sides fo another triangle, the triangles are congruent
- Theorem 55 (law of cosines)
- if the sides opposite
- Theorem 4 (supplements)
- supplements of the same angle are equal
- Theorem 54 (law of sines)
- if the sides opposite
- Theorem 33
- the diagonals of a rectangle are equal
- Theorem 45 (aa)
- if two angles of one triangle are equal to two angles of another triangle, the triangles are similar
- Theorem 35
- the base angles of an isosceles trapezoid are equal
- Theorem 30
- a quadrilateral is a parallelogram if its diagonals bisect each other
- Theorem 39
- the area of a triangle is half the product of any base and its corresponding altitude
- Theorem 34
- the diagonals of a rhombus are perpendicular
- Theorem 50 (Isosceles Right Triangle)
- in an isosceles right triangle, the hypotenuse is the square root of two times the length of a leg
- Theorem 48
- the ratio of the areas of two similar polygons is equal to the square of the ratio of the corresponding sides
- Theorem 22 (aas)
- if two angles and the side opposite one of them in one triangle are equal to the corresponding parts of another right triangle, the triangles are congruent
- Theorem 58
- the perpendicular bisector of a chord of a circle contains the center of the circle
- Theorem 44 (side splitter)
- if a line parallel to one side of a triangle intersects the other two sides in different points, it divides the sides in the same ratio
- Theorem 47
- the ratio of the perimeters of two similar polygons is equal to the ratio of the corresponding sides
- Theorem 38
- the area of a right triangle is half the product of its legs