# Trigonometry

Videos on trigonometry. Watch the "Geometry" playlist first if you have trouble understanding the topics covered here.

• ##### Basic Trigonometry Part 1
Salman Khan

An introduction to trigonometric functions: sine, cosine, and tangent.

• ##### Basic Trigonometry Part 2
Salman Khan

Another example of figuring out the sine, cosine, and tangent of an angle in a right triangle.

Salman Khan

• ##### Using Trig Functions Part 1
Salman Khan

Using Trigonometric functions to solve the sides of a right triangle.

• ##### Using Trig Functions Part 2
Salman Khan

A couple of more examples of using Trig functions to solve the sides of a triangle.

• ##### The Unit Circle Definition of Trigonometric Functions Part 1
Salman Khan

Using the unit circle to extend the SOH CAH TOA definition of the basic trigonometric functions.

• ##### The Unit Circle Definition of Trigonometric Functions Part 2
Salman Khan

Using the unit circle to define the sine, cosine, and tangent functions.

• ##### Graph of the Sine Function
Salman Khan

Using the unit circle definition of the sine function to make a graph of it.

• ##### Graph of the Trig Function
Salman Khan

Exploring the graphs of trig functions.

• ##### Graphing Trig Functions
Salman Khan

Analyzing the amplitude and periods of the sine and cosine functions.

• ##### Trig Graphs
Salman Khan

Determining the equations of trig functions by inspecting their graphs.

• ##### Determining the Equation of a Trigonometric Function
Salman Khan

Determining the amplitude and period of sine and cosine functions.

• ##### Trigonometric Identities Part 1
Salman Khan

Introduction to trigonometric identities.

• ##### Proof: sin(a+b) = (cos a)(sin b) + (sin a)(cos b)
Salman Khan

Proof of the trig identity sin(a+b) = (cos a)(sin b) + (sin a)(cos b).

• ##### Proof: cos(a+b) = (cos a)(cos b)-(sin a)(sin b)
Salman Khan

Proof of the trig identity: cos(a+b) = (cos a)(cos b)-(sin a)(sin b).

• ##### Trigonometric Identities Part 2
Salman Khan

More playing around with trig identities.

• ##### Trigonometric Identities Part 3
Salman Khan

Continuation of the playing around with trig identities.

• ##### Trigonometry Word Problems Part 1
Salman Khan

The first part of a problem when the captain of a ship goes off track.

• ##### Trigonometry Word Problems Part 2
Salman Khan

The second part of the problem of the off-track ship captain.

• ##### Law of Cosines
Salman Khan

Introduction to the law of cosines to solve for a side of a triangle when 2 sides and an angle are known.

Salman Khan

Trigonometry problem involving two ships colliding.

• ##### Proof: Law of Sines
Salman Khan

A simple proof of the Law of Sines.

• ##### Ferris Wheel Trig Problem Part 1
Salman Khan

Trigonometry problems dealing with the height of two people on a ferris wheel.

• ##### Ferris Wheel Trig Problem Part 2
Salman Khan

Part 2 of the ferris wheel problems. Graph of h(t)=9-8cos(18t).

• ##### Fun Trig Problem
Salman Khan

A trig problem involving the quadratic equation.

• ##### Inverse Trig Functions: Arcsin
Salman Khan

Introduction to the inverse trig function arcsin.

• ##### Inverse Trig Functions: Arctan
Salman Khan

Understanding the arctan or inverse tangent function.

• ##### Inverse Trig Functions: Arccos
Salman Khan

Understanding the inverse cosine or arccos function.

• ##### Trigonometry Identity Review/Fun
Salman Khan

Revisiting the proofs of some trigonometry identities.