We saw how you can use **trigonometry** to find the **components of a vector**. If a car’s velocity vector is 45 mph at a 30 degree angle to the x-axis, you can use the cosine of 30 to figure out it’s moving 39 mph in the x-direction. Using the **sine of 30** you can find it’s going **22.5 mph in the y-direction**.

A way to write this mathematically is with *i* and *j* notation. The letters *i* and *j* are unit vectors in the x and y direction respectively. The x component is multiplied times *i* and the y component is multiplied times *j*. Our vector for a car moving at 45 mph at a 30 degree angle is formally written as **v = 39***i* + 22.5*j* and you can include the mph (units) if you want to be super correct.