# Question #cd107

##### 2 Answers

Jan 31, 2015

Let's first draw a triangle to get the trigonometry right.

We'll use

So we get:

Which is the definition of the **sine** .

**Answer** :

**Extra**

You could have done this another way if you knew that

Then it would be:

*(picture: Wikipedia)*

Nov 7, 2017

#### Answer:

# cosx tanx -= sinx #

#### Explanation:

# cosx tanx -= cosx * sinx/cosx -= sinx #