# Homework Help: Polar points in rectangular coordinates help

1. Mar 11, 2006

### lakitu

My teacher has told me I will need to be able to do these in my up and comping exam later this month. He covered the topic a while ago but I didn't quite understand. Here is an example I have.

Express the polar point (6, 120 °) in rectangular coordinates.

I have no idea how to start doing these? Guidence of any kind would be wonderful.

Regards Lakitu

2. Mar 11, 2006

### assyrian_77

Surely you know the relation between cartesian coordinates and polar coordinates? It is two very simple equations that express x and y in r and $\theta$.

3. Mar 11, 2006

### lakitu

Sorry to dissapoint, I have no idea how to do these

Lakitu

4. Mar 11, 2006

### topsquark

I fail to see how your teacher would expect you to be able to do this problem if (s)he didn't give you the above mentioned equations. Look in your book or notes under "polar coordinates."

-Dan

5. Mar 11, 2006

### VietDao29

The relation between Rectangular coordinate, and Polar coordinate is:
$$\begin{array}{l} x = r \cos \theta \\ y = r \sin \theta \end{array}$$
Now what's r, and what's $$\theta$$? From there, can you find x, y?
Can you go from here? :)

6. Mar 11, 2006

### lakitu

Thank you for your help VietDao. Big Help. ok i have come up with the answers x = -3 and y = 5.196. I have drawn a triangle also and this seems to be the same.

Thanks again

7. Mar 12, 2006

### VietDao29

Yes, it looks good. However, I'd prefer the y to be:
$$y = 3 \sqrt{3}$$ instead of an approximation. Other than that, everything seems correct. :)