• #### 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 Double-Angle Formulas - Problem 1

##### Math›Trigonometry›Advanced Trigonometry
How to use the sine and cosine double-angle formulas to find sin(2a) and cos(2a) when sin(a) is known.
• #### The Double-Angle Formulas - Problem 1

##### Math›Precalculus›Advanced Trigonometry
How to use the sine and cosine double-angle formulas to find sin(2a) and cos(2a) when sin(a) is known.
• #### The Double-Angle Formulas - Problem 2

##### Math›Trigonometry›Advanced Trigonometry
How to derive a triple-angle formula for cosine.
• #### The Double-Angle Formulas - Problem 2

##### Math›Precalculus›Advanced Trigonometry
How to derive a triple-angle formula for cosine.
• #### The Half-Angle Identities - Problem 3

##### Math›Precalculus›Advanced Trigonometry
How to use the double-angle formulas for sine and cosine to derive a half-angle formula for tangent.
• #### The Half-Angle Identities - Problem 3

##### Math›Trigonometry›Advanced Trigonometry
How to use the double-angle formulas for sine and cosine to derive a half-angle formula for tangent.
• #### The Euler Formula - Problem 3

##### Math›Precalculus›Polar Coordinates and Complex Numbers
How to derive two trigonometric identities using Euler's Formula.