# convert polar coordinates to rectangular coordinates

• Feb 3rd 2009, 02:48 PM
sonia1
convert polar coordinates to rectangular coordinates
i've been working on this following question for ages and I wondered if anyone can help

The curve is defined in the polar coordinates:

http://www.mathhelpforum.com/math-he...97a8c47a-1.gif = 3/(1+cos(phi))

write the equation for this curve in the cartesian system of coordinates.

plot this curve. what is the name of the curve?

I probably can do the last bits once I can get the equation
• Feb 3rd 2009, 03:47 PM
mylestone
Move your $1+cos(\theta)$ to the other side of the equation. You'll use the relationships $x=r \cdot cos(\theta)$ and $r = \sqrt{x^2 + y^2}$ to substitute a couple of things (so that you're only playing with $x$'s and $y$'s) before you simplify and graph your result.
• Feb 4th 2009, 12:34 AM
sonia1
i did not but I couldn't solve it in cartesian form
• Feb 4th 2009, 12:48 AM
mr fantastic
Quote:

Originally Posted by sonia1
i did not but I couldn't solve it in cartesian form

If you follow the good advice given then you have $\rho + \rho \cos \phi = 3 \Rightarrow \sqrt{x^2 + y^2} + x = 3 \Rightarrow \sqrt{x^2 + y^2} = 3 - x$ and you should see what to do next.
• Feb 4th 2009, 12:55 AM
sonia1
that's what I got up to but couldn't do the next bit
• Feb 4th 2009, 01:10 AM
mr fantastic
Quote:

Originally Posted by sonia1
that's what I got up to but couldn't do the next bit

It would save time if you said where you got up to and where you were stuck.

Now you square both sides and then simplify.
• Feb 4th 2009, 01:12 AM
mylestone
Quote:

Originally Posted by sonia1
that's what I got up to but couldn't do the next bit

Get rid o' the square root.