# [SOLVED] Convert polar coordinates to rectangular

• Apr 16th 2008, 03:28 PM
bilbobaggins
[SOLVED] Convert polar coordinates to rectangular
1. $r=-3*sintheta$
2. $r*sectheta=3$

How do you make these into rectangular equations?
• Apr 16th 2008, 03:40 PM
mr fantastic
Quote:

Originally Posted by bilbobaggins
1. $r=-3*sintheta$
2. $r*sectheta=3$

How do you make these into rectangular equations?

1. $r = - 3 \sin \theta \Rightarrow r^2 = -3 r \sin \theta$ ......

2. $r \sec \theta = 3 \Rightarrow \frac{r}{\cos \theta} = 3 \Rightarrow r = 3 \cos \theta$. Now use what you've learned from how I did 1.
• Apr 16th 2008, 03:45 PM
bilbobaggins
Quote:

Originally Posted by mr fantastic
1. $r = - 3 \sin \theta \Rightarrow r^2 = -3 r \sin \theta$ ......

2. $r \sec \theta = 3 \Rightarrow \frac{r}{\cos \theta} = 3 \Rightarrow r = 3 \cos \theta$. Now use what you've learned from how I did 1.

I had already gotten to where you did in 2. 1 is still troubling me though, so you just multiplied both sides by r?
• Apr 16th 2008, 03:54 PM
mr fantastic
Quote:

Originally Posted by bilbobaggins
I had already gotten to where you did in 2. 1 is still troubling me though, so you just multiplied both sides by r?

That's what I did in 1, right? And after doing this, is it obvious what comes next?
• Apr 16th 2008, 04:00 PM
bilbobaggins
Quote:

Originally Posted by mr fantastic
That's what I did in 1, right? And after doing this, is it obvious what comes next?

x^2+y^2=-3y?
• Apr 16th 2008, 04:26 PM
mr fantastic
Quote:

Originally Posted by bilbobaggins
x^2+y^2=-3y?

(Clapping) (number 1, I assume)