• #### The Definitions of Sine and Cosine - Concept

##### Math›Trigonometry›Trigonometric Functions
How we define sine and cosine for all angle measures using the unit circle.
• #### The Definitions of Sine and Cosine - Concept

##### Math›Precalculus›Trigonometric Functions
How we define sine and cosine for all angle measures using the unit circle.
• #### The Cosine Addition Formulas - Concept

How to derive the cosine of a difference formula.
• #### The Cosine Addition Formulas - Problem 1

How to use the cosine of a difference formula to simplify an expression or to find the cosine of an angle.
• #### The Cosine Addition Formulas - Problem 1

How to use the cosine of a difference formula to simplify an expression or to find the cosine of an angle.
• #### The Inverse Cosine Function - Problem 2

How to use apply the inverse identities for cosine.
• #### The Cosine Addition Formulas - Concept

How to derive the cosine of a difference formula.
• #### The Inverse Cosine Function - Problem 2

How to use apply the inverse identities for cosine.
• #### The Law of Cosines - Concept

##### Math›Trigonometry›Basic Trigonometry
How to define and use the law of cosines.
• #### The Law of Cosines - Concept

##### Math›Geometry›Basic Trigonometry
How to define and use the law of cosines.
• #### The Law of Cosines - Concept

##### Math›Precalculus›Basic Trigonometry
How to define and use the law of cosines.
• #### The Law of Cosines - Problem 1

##### Math›Precalculus›Basic Trigonometry
How to use the law of cosines to find a missing side in a triangle.
• #### The Law of Cosines - Problem 1

##### Math›Geometry›Basic Trigonometry
How to use the law of cosines to find a missing side in a triangle.
• #### The Law of Cosines - Problem 1

##### Math›Trigonometry›Basic Trigonometry
How to use the law of cosines to find a missing side in a triangle.
• #### The Cosine Addition Formulas - Problem 2

How to derive the cosine of a sum formula and use it to find the cosine of an angle.
• #### The Cosine Addition Formulas - Problem 2

How to derive the cosine of a sum formula and use it to find the cosine of an angle.
• #### Evaluating Sine and Cosine at Other Special Angles - Concept

##### Math›Trigonometry›Trigonometric Functions
How to measure the sine and cosine of 150.
• #### Evaluating Sine and Cosine at Special Acute Angles - Problem 2

##### Math›Trigonometry›Trigonometric Functions
How to measure sine and cosine of pi/3