- #1

- 20

- 0

## Homework Statement

How do you convert the rectangular coordinate points (1, -2) to polar form?

note: rectangular is (x,y) polar is (r, theta)

## Homework Equations

r^2 = x^2 + y^2 , x = rcos(theta) , y = rsin(theta) , tan(theta) = y/x

## The Attempt at a Solution

So basically, I tried getting it to polar form by first finding the radius. This part was easy since all I had to do was to plug it into the first equation.

r^2 = (1)^2 + (-2)^2

= sqrt(5)

Next, I tried getting theta by getting tan(theta).

tan(theta) = -2/1

Here is where the problem came in. When I tried putting this onto the unit circle, I didn't get any recognizable triangles(such as the 45-45 right triangle or the 30-60-90 right triangle).

So how would I find theta?(without using calculator)

Last edited: