• #### Solving Trigonometric Equations - Problem 1

How to solve a simple cosine equation: cos x = ?2/2.
• #### The Sine Addition Formulas - Problem 2

How to derive the sine of a difference formula and use it to find the sine of an angle.
• #### Square Matrices - Problem 3

##### Math›Precalculus›Systems of Linear Equations and Matrices
How to show that two matrices are inverses (in the sense of matrix multiplication).
• #### Solving Trigonometric Equations - Problem 1

How to solve a simple cosine equation: cos x = ?2/2.
• #### Solving Trigonometric Equations - Problem 3

How to solve a simple trig equation involving secant.
• #### Other Forms of the Cosine Double-Angle Formula - Concept

How to derive two more cosine double-angle formulas.
• #### The Number e and the Natural Logarithm - Problem 2

##### Math›Precalculus›Exponential and Logarithmic Functions
How to evaluate natural logarithms of e to a power.
• #### The Inverse of a Square Matrix - Problem 2

##### Math›Precalculus›Systems of Linear Equations and Matrices
How to determine that a matrix has no inverse using row operations.
• #### The Inverse of a Square Matrix - Problem 1

##### Math›Precalculus›Systems of Linear Equations and Matrices
How to find the inverse of a square matrix of order 2 using row operations.
• #### The Inverse of a Square Matrix - Problem 3

##### Math›Precalculus›Systems of Linear Equations and Matrices
How to find the inverse of a square matrix of order 3 using row operations.