Skip to main content

The Educator's Academy

Helping to transform education and ourselves.

Public Education Today
Government 12th Grade
Global History
US History
Integrated Algebra
Innovations & Curriculum
Technology & Education
ES BOCES Summer School
Moneyball & Education
Grade 6 Social Studies
Member Login
Site Map
An unbelievable review site for all basic and intermediate math functions:
Be sure to complete these exercises if you need remediation.  Remember, you have to be able to walk before you can run.

"Videos on geometry" from Khan Academy (


Recent NYS Geometry Regents exams -


1.                                       Basic Language and Notation of Geometry

2.                                       Lines, Line Segments, and Rays

3.                                       Language and Notation of the Circle

4.                                       Angle Basics

5.                                       Measuring Angles in Degrees

6.                                       Using a Protractor

7.                                       Measuring Angles

8.                                       Complementary and Supplementary Angles

9.                                       Angles at the intersection of two lines

10.                                   Proof-Vertical Angles are Equal

11.                                   Angles Formed by Parallel Lines and Transversals

12.                                   Proof - Sum of Measures of Angles in a Triangle are 180

13.                                   Triangle Angle Example 1

14.                                   Triangle Angle Example 2

15.                                   Triangle Angle Example 3

16.                                   Challenging Triangle Angle Problem

17.                                   Proof - Corresponding Angle Equivalence Implies Parallel Lines

18.                                   Finding more angles

19.                                   Sum of Interior Angles of a Polygon

20.                                   Congruent Triangles and SSS

21.                                   SSS to Show a Radius is Perpendicular to a Chord that it Bisects

22.                                   Other Triangle Congruence Postulates

23.                                   Two column proof showing segments are perpendicular

24.                                   Sum of the exterior angles of convex polygon

25.                                   Finding Congruent Triangles

26.                                   More on why SSA is not a postulate

27.                                   Congruent Triangle Proof Example

28.                                   Congruent Triangle Example 2

29.                                   Congruent legs and base angles of Isosceles Triangles

30.                                   Equilateral Triangle Sides and Angles Congruent

31.                                   Equilateral and Isosceles Example Problems

32.                                   Another Isosceles Example Problem

33.                                   Example involving an isosceles triangle and parallel lines

34.                                   Figuring out all the angles for congruent triangles example

35.                                   Perimeter and Area Basics

36.                                   Triangle Area Proofs

37.                                   Interesting Perimeter and Area Problems

38.                                   Koch Snowflake Fractal

39.                                   Area of an Equilateral Triangle

40.                                   Area of Koch Snowflake (part 1) - Advanced

41.                                   Area of Koch Snowflake (part 2) - Advanced

42.                                   Challenging Perimeter Problem

43.                                   Similar Triangle Basics

44.                                   Similarity Postulates

45.                                   Similar Triangle Example Problems

46.                                   Similarity Example Problems

47.                                   Challenging Similarity Problem

48.                                   Similarity example where same side plays different roles

49.                                   Finding Area Using Similarity and Congruence

50.                                   Pythagorean Theorem Proof Using Similarity

51.                                   30-60-90 Triangle Side Ratios Proof

52.                                   45-45-90 Triangle Side Ratios

53.                                   30-60-90 Triangle Example Problem

54.                                   The Golden Ratio

55.                                   Introduction to angles (old)

56.                                   Angles (part 2)

57.                                   Angles (part 3)

58.                                   Angles formed between transversals and parallel lines

59.                                   Angles of parallel lines 2

60.                                   The Angle Game

61.                                   Similar triangles

62.                                   Similar triangles (part 2)

63.                                   Angle Game (part 2)

64.                                   Acute Right and Obtuse Angles

65.                                   Area and Perimeter

66.                                   Circles: Radius, Diameter and Circumference

67.                                   Area of a circle

68.                                   The Pythagorean Theorem

69.                                   Pythagorean Theorem II

70.                                   45-45-90 Triangles

71.                                   Intro to 30-60-90 Triangles

72.                                   30-60-90 Triangles II

73.                                   Solid Geometry Volume

74.                                   Cylinder Volume and Surface Area

75.                                   Heron's Formula

76.                                   Part 1 of Proof of Heron's Formula

77.                                   Part 2 of the Proof of Heron's Formula

78.                                   Inscribed and Central Angles

79.                                   Area of Inscribed Equilateral Triangle (some basic trig used)

80.                                   Right Triangles Inscribed in Circles (Proof)

81.                                   Area of Diagonal Generated Triangles of Rectangle are Equal

82.                                   Triangle Medians and Centroids

83.                                   Triangle Medians and Centroids (2D Proof)

84.                                   Rhombus Diagonals

85.                                   2003 AIME II Problem 7

86.                                   Perpendicular Radius Bisects Chord

87.                                   Circumcenter of a Triangle

88.                                   Circumcenter of a Right Triangle

89.                                   Three Points Defining a Circle

90.                                   Point Line Distance and Angle Bisectors

91.                                   Incenter and incircles of a triangle

92.                                   Angle Bisector Theorem Proof

93.                                   Inradius Perimeter and Area

94.                                   Angle Bisector Theorem Examples

95.                                   Medians divide into smaller triangles of equal area

96.                                   Exploring Medial Triangles

97.                                   Proving that the Centroid is 2-3rds along the Median

98.                                   Median Centroid Right Triangle Example

99.                                   Proof - Triangle Altitudes are Concurrent (Orthocenter)

100.                                Review of Triangle Properties

101.                                Euler Line

102.                                Euler's Line Proof

103.                                Common Orthocenter and Centroid

104.                                Quadrilateral Overview

105.                                Proof - Opposite Sides of Parallelogram Congruent

106.                                Proof - Diagonals of a Parallelogram Bisect Each Other

107.                                Proof - Opposite Angles of Parallelogram Congruent

108.                                Proof - Rhombus Diagonals are Perpendicular Bisectors

109.                                Proof - Rhombus Area Half Product of Diagonal Length

110.                                Area of a Parallelogram

111.                                Problem involving angle derived from square and circle

112.                                Area of a Regular Hexagon


New York State Geometry Regents Review


Click on the second demo video for all different pictures of angles.