# How do you prove #sin3x = 3sinx - 4sin^3x#?

##### 2 Answers

#### Answer

#### Answer:

#### Explanation

#### Explanation:

Since the angle sum formula of sine is:

and the double angle formula of cosine:

then:

#### Answer

#### Answer:

#### Explanation

#### Explanation:

Describe your changes (optional) 200

#### Answer:

we can use DeMoivre's theorem

#### Explanation:

since we want

from

equating imaginary parts

but

as required

Describe your changes (optional) 200