Geometry

Triangles

  1. Proof - Sum of Measures of Angles in a Triangle are 180
  2. Triangle Angle Example 1
  3. Triangle Angle Example 2
  4. Triangle Angle Example 3
  5. Challenging Triangle Angle Problem
  6. Congruent and Similar Triangles
  7. Congruent Triangles and SSS
  8. SSS to Show a Radius is Perpendicular to a Chord that it Bisects
  9. Other Triangle Congruence Postulates
  10. Finding Congruent Triangles
  11. More on why SSA is not a postulate
  12. Congruent Triangle Proof Example
  13. Congruent Triangle Example 2
  14. Congruent legs and base angles of Isosceles Triangles
  15. Equilateral Triangle Sides and Angles Congruent
  16. Equilateral and Isosceles Example Problems
  17. Another Isosceles Example Problem
  18. Example involving an isosceles triangle and parallel lines
  19. Figuring out all the angles for congruent triangles example
  20. Triangle Area Proofs
  21. Area of an Equilateral Triangle
  22. Koch Snowflake Fractal
  23. Area of Koch Snowflake (part 1) - Advanced
  24. Area of Koch Snowflake (part 2) - Advanced
  25. Similar Triangle Basics
  26. Similarity Postulates
  27. Similar triangles
  28. Similar triangles (part 2)
  29. Similar Triangle Example Problems
  30. Similarity Example Problems
  31. Application of Similar Triangles
  32. Challenging Similarity Problem
  33. Similarity example where same side plays different roles
  34. Finding Area Using Similarity and Congruence
  35. Introduction to the Pythagorean Theorem
  36. The Pythagorean Theorem
  37. Pythagorean Theorem II
  38. Pythagorean Theorem 1
  39. Pythagorean Theorem 2
  40. Pythagorean Theorem 3
  41. Garfield's proof of the Pythagorean Theorem
  42. Bhaskara's proof of Pythagorean Theorem
  43. Pythagorean Theorem Proof Using Similarity
  44. Another Pythagorean Theorem Proof
  45. 45-45-90 Triangles
  46. 45-45-90 Triangle Side Ratios
  47. Intro to 30-60-90 Triangles
  48. 30-60-90 Triangles II
  49. 30-60-90 Triangle Side Ratios Proof
  50. 30-60-90 Triangle Example Problem
  51. Heron's Formula
  52. Part 1 of Proof of Heron's Formula
  53. Part 2 of the Proof of Heron's Formula
  54. Area of Inscribed Equilateral Triangle (some basic trig used)
  55. Right Triangles Inscribed in Circles (Proof)
  56. Area of Diagonal Generated Triangles of Rectangle are Equal
  57. Circumcenter of a Triangle
  58. Circumcenter of a Right Triangle
  59. Incenter and incircles of a triangle
  60. Medians divide into smaller triangles of equal area
  61. Exploring Medial Triangles
  62. Proving that the Centroid is 2-3rds along the Median
  63. Median Centroid Right Triangle Example
  64. Proof - Triangle Altitudes are Concurrent (Orthocenter)
  65. Review of Triangle Properties
  66. Euler Line
  67. Euler's Line Proof
  68. Common Orthocenter and Centroid
  69. Basic Triangle Proofs Module Example
  70. Basic Triangle Proofs Module Example 2
  71. Fill-in-the-blank triangle proofs example 1
  72. Wrong statements in proofs example 1
  73. Fill-in-the-blank triangle proofs example 2

Another Isosceles Example Problem Possible angles for an isosceles triangle

Back

Another Isosceles Example Problem

⇐ Use this menu to view and help create subtitles for this video in many different languages. You'll probably want to hide YouTube's captions if using these subtitles.

Discuss the site

For general discussions about Khan Academy, visit our Reddit discussion page.


Flag inappropriate posts

Here are posts to avoid making. If you do encounter them, flag them for attention from our Guardians.

abuse
  • disrespectful or offensive
  • an advertisement
not helpful
  • low quality
  • not about the video topic
  • soliciting votes or seeking badges
  • a homework question
  • a duplicate answer
  • repeatedly making the same post
wrong category
  • a tip or feedback in Questions
  • a question in Tips & Feedback
  • an answer that should be its own question
about the site