Course

# Geometry

Videos on geometry. Basic understanding of Algebra I necessary. After this, you'll be ready for Trigonometry.

## 22 Lectures

• ### Introduction to Angles

00:09:55

Salman Khan, GeometryKhan Academy

What an angle is. Angles in a circle. Complementary and supplementary angles.

• ### Angles Part 2

00:09:04

Salman Khan, GeometryKhan Academy

More on complementary and supplementary angles. Introduction to opposite angles.

• ### Angles Part 3

00:09:47

Salman Khan, GeometryKhan Academy

Angles formed when a transversal intersects parallel lines.

• ### Angles Formed Between Transversals and Parallel Lines

00:07:53

Salman Khan, GeometryKhan Academy

Angles of parallel lines.

• ### Angles of Parallel Lines 2

00:05:15

Salman Khan, GeometryKhan Academy

Angles of parallel lines examples.

• ### The Angle Game

00:09:01

Salman Khan, GeometryKhan Academy

Using what we know to solve for angles in the Angle Game.

• ### Similar Triangles

00:09:34

Salman Khan, GeometryKhan Academy

Introduction to similar triangles.

• ### Similar Triangles 2

00:09:54

Salman Khan, GeometryKhan Academy

More on similar triangles.

• ### Area and Perimeter

00:12:20

Salman Khan, GeometryKhan Academy

Area of rectangles and triangles. Perimeter of rectangles.

• ### Circles: Radius, Diameter, and Circumference

00:11:05

Salman Khan, GeometryKhan Academy

Understanding the relationship between the radius diameter and circumference of a circle.

• ### The Pythagorean Theorem

00:10:46

Salman Khan, GeometryKhan Academy

Introduction to the Pythagorean Theorem.

• ### The Pythagorean Theorem II

00:09:36

Salman Khan, GeometryKhan Academy

More Pythagorean Theorem examples. Introduction to 45-45-90 triangles.

• ### 45-45-90 Triangles

00:09:30

Salman Khan, GeometryKhan Academy

Introduction to 45-45-90 Triangles.

• ### Intro to 30-60-90 Triangles

00:09:39

Salman Khan, GeometryKhan Academy

A few more 45-45-90 examples and an introduction to 30-60-90 triangles.

• ### 30-60-90 Triangles II

00:04:49

Salman Khan, GeometryKhan Academy

More examples using 30-60-90 triangles.

• ### Heron's Formula

00:04:43

Salman Khan, GeometryKhan Academy

Using Heron's Formula to determine the area of a triangle while only knowing the lengths of the sides.

• ### Part 1 of Proof of Heron's Formula

00:10:59

Salman Khan, GeometryKhan Academy

Part 1 of the proof of Heron's Formula.

• ### Part 2 of Proof of Heron's Formula

00:12:08

Salman Khan, GeometryKhan Academy

Showing that the expression in part 1 is identical to Heron's Formula.

• ### An Inscribed Angle is Half of a Central Angle that Subtends the Same Arc

00:14:16

Salman Khan, GeometryKhan Academy

Showing that an inscribed angle is half of a central angle that subtends the same arc.

• ### Area of Inscribed Equilateral Triangle (Some Basic Trig Used) 2

00:11:39

Salman Khan, GeometryKhan Academy

Problem that requires us to figure out the area of an equilateral triangle inscribed in a circle (A little trigonometry used).

• ### Right Triangles Inscribed in Circles

00:05:35

Salman Khan, GeometryKhan Academy

Proof showing that a triangle inscribed in a circle having a diameter as one side is a right triangle.

• ### Area of Inscribed Equilateral Triangle (Some Basic Trig Used)

00:04:36

Salman Khan, GeometryKhan Academy

Area of Diagonal Generated Triangles of Rectangle are Equal.