• #### The Cosine Addition Formulas - Problem 2

##### Math›Precalculus›Advanced Trigonometry
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

##### Math›Trigonometry›Advanced Trigonometry
How to derive the cosine of a sum formula and use it to find the cosine of an angle.
• #### The Cosine Addition Formulas - Problem 3

##### Math›Trigonometry›Advanced Trigonometry
How to evaluate cos(a ? b) and cos(a + b) when you know only sin(a) and cos(b).
• #### The Cosine Addition Formulas - Problem 3

##### Math›Precalculus›Advanced Trigonometry
How to evaluate cos(a ? b) and cos(a + b) when you know only sin(a) and cos(b).
• #### The Double-Angle Formulas - Concept

##### Math›Trigonometry›Advanced Trigonometry
How to use the sine and cosine addition formulas to prove the double-angle formulas.
• #### The Double-Angle Formulas - Concept

##### Math›Precalculus›Advanced Trigonometry
How to use the sine and cosine addition formulas to prove the double-angle formulas.
• #### The Sine Addition Formulas - Concept

##### Math›Precalculus›Advanced Trigonometry
How to derive the sine of a sum formula.
• #### The Sine Addition Formulas - Concept

##### Math›Trigonometry›Advanced Trigonometry
How to derive the sine of a sum formula.