# Trigonometric Identities

### Trigonometric Identities

Now that we know the definitions of the trigonometric functions, and have a clear understanding how they behave as an angle changes, we can explore the relationships that exist between them.

A trigonometric identity is an equation involving trigonometric functions that can be solved by any angle. Trigonometric identities have less to do with evaluating functions at specific angles than they have to do with relationships between functions. Eight specific trigonometric identities are fundamental. These can be used to form an infinite number of other identities. We'll take a look at the eight fundamental trigonometric identities, and then some additional identities concerning negative angles (angles in which the rotation between the initial and terminal side is clockwise). Using the identities we'll learn, we can manipulate trigonometric expressions and simplify them if they're complicated. Finally, we'll review what we know so far of trigonometry before we move on to study how to solve triangles and trigonometric equations.

## Take a Study Break

### What's your Pretty Little Liars name?

Take this quiz to find out!

### Which young actress just got married?

Click to find out!

### Cat bearding WINS THE INTERNET

Have you seen this yet?

### Scary movies with funny posters

These. Are. Hilarious.

### Geeky Actors: Then and Now

Travel back in time!

### Villains We Want These Actresses to Play

From super cute to super bad!

### 10 Movies Better Than Their Books

What do you think?