• #### Bonus Math Content

##### Test Prep›ACT›ACT Math
Short, helpful video on ACT Trigonometry by top ACT prep instructor, Devorah. Videos are produced by leading online education provider, Brightstorm.
• #### Trigonometric Equations that Require Factoring - Concept

How to solve a sine equation by factoring: 4 [sin(theta)]^2 = 2.
• #### The Cosine Addition Formulas - Problem 3

How to evaluate cos(a ? b) and cos(a + b) when you know only sin(a) and cos(b).
• #### Using the Inverse Trigonometric Functions - Problem 1

How to prove an identity that involves sin^-1(x) and cos^-1(x).
• #### Other Forms of the Cosine Double-Angle Formula - Concept

How to derive two more cosine double-angle formulas.
• #### Using the Sine and Cosine Addition Formulas to Prove Identities - Problem 2

How to use the sine and cosine supplementary angle identities.
• #### Trigonometric Equations that Require Factoring - Problem 2

How to solve a tangent equation by factoring: tan^2(x) - tan(x) - 2 = 0.
• #### Trigonometric Equations that Require Factoring - Problem 3

How to solve a sine and cosine equation by factoring: ?2 sin2 x ? 5 cos x + 4 = 0.
• #### Using the Sine and Cosine Addition Formulas to Prove Identities - Concept

How to use the sine and cosine addition formulas to prove the cofunction identities.
• #### Trigonometric Equations that Require Factoring - Problem 1

How to solve a sine equation by factoring: 2 sin2 x ? 3 sin x + 1 = 0.
• #### Using the Sine and Cosine Addition Formulas to Prove Identities - Problem 1

How to use the sine and cosine addition formulas to prove the "add pi" identities.
• #### Other Forms of the Cosine Double-Angle Formula - Problem 1

How to use the cosine double-angle formulas to derive the power reduction formulas.
• #### Using the Sine and Cosine Addition Formulas to Prove Identities - Problem 3

How to use the sine and cosine addition formulas to prove a difference formula for tangent.
• #### Other Forms of the Cosine Double-Angle Formula - Problem 2

How to use the power reduction formulas to reduce cos4 x.
• #### Angle of Elevation and Depression - Concept

##### Math›Precalculus›Basic Trigonometry
How to define an angle of elevation or an angle of depression.
• #### Angle of Elevation and Depression - Concept

##### Math›Geometry›Basic Trigonometry
How to define an angle of elevation or an angle of depression.
• #### Trigonometric Ratios: Sine - Concept

##### Math›Geometry›Basic Trigonometry
How to define the sine ratio and identify the sine of an angle in a right triangle.
• #### The Tangent Function - Concept

##### Math›Trigonometry›Trigonometric Functions
How to define the tangent function for all angles.
• #### Trigonometric Ratios: Cosine - Problem 2

##### Math›Geometry›Basic Trigonometry
How to find the length of a hypotenuse in a right triangle, given a side length.
• #### Angle of Elevation and Depression - Problem 1

##### Math›Precalculus›Basic Trigonometry
How to use an angle of depression to solve a word problem with an airplane.