# More Trigonometric Identities

### Multiple Angles and Functions

Up until now, this text has dealt with trigonometric functions of single angles, and basic trigonometric identities. In the following lessons, we'll discuss trigonometric functions of multiple angles, and identities of multiple trigonometric functions.

When you have a single function and a single angle, calculations are easy. Even when the angle is a variable, a graph quite easily illustrates how the functions of the variable angle will behave. Therefore, as we learn formulas for calculating values of functions of angle sums, products, and sums and products of different functions, you may wonder why such formulas are necessary or useful. But the formulas (identities, actually, because they're true for all angles) we'll learn over the following sections help simplify complicated double-variable trigonometric equations and thereby allow us to calculate those double-variable equations through the more simple techniques we've already seen. With this knowledge, the field of trigonometry will become so wide open, you'll have to wear shades.

## Take a Study Break

### Star Trek gets SEXY

Chris Pine and Zoe Saldana heat up the red carpet!

### Are you afraid of relationships?

Auntie SparkNotes can help!

### Sexy starlet style

See every single look from the Met Gala!

### 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?

### How To Look Like J-Law...

When you don't look like J-Law.

### 12 Scientific Inaccuracies in Into Darkness

What did Star Trek get wrong?

## The Book

### Read What You Love, Anywhere You Like

Get Our FREE NOOK Reading Apps