# Thread: Polar coordinates

1. ## Polar coordinates

Find the polar coordinates corresponding to the point for which the rectangular coordinates are (2,-5), correct to 3 significant digits.

How do I start this problem?

2. Polar coordinates are $\displaystyle (r, {\theta})$

Therefore, $\displaystyle r=\sqrt{2^{2}+(-5)^{2}}$

$\displaystyle {\theta}=tan^{-1}(\frac{-5}{2})$

3. $\displaystyle r = 5.39$

$\displaystyle \theta = -68.2\;degrees\Longrightarrow 360 + -68.2 = 291.8\;degrees$

Should I write my answer has $\displaystyle (5.39,\;291.8\;degrees)$

Or change the $\displaystyle 291.8\;degrees$ to radians?

Which would give $\displaystyle 291.8 \;degrees = 5.09 \;radians$

So the answer would be $\displaystyle (5.39,\; 5.09\; radians)$? Or the first one I listed?

4. Polar coordinates are generally given in degrees instead of radians.

5. Originally Posted by galactus
Polar coordinates are generally given in degrees instead of radians.
I really doubt that that is a true statement.
I for one, advocate dropping the use of degrees in mathematics.
My rational is simple: radians are numbers.

6. You are certainly right, Plato. I don't know what's wrong with me. Must've been a brain fart. I was actually thinking the other way, but posted the opposite.

7. Should I write my answer as this $\displaystyle (5.39,\; 5.09\; radians)$ or $\displaystyle (5.39,\;5.09)$

Should I write radians in my answer or no?

8. Originally Posted by Shinjiro
Should I write my answer as this $\displaystyle (5.39,\; 5.09\; radians)$ or $\displaystyle (5.39,\;5.09)$

Should I write radians in my answer or no?
These questions have been addressed via response to pm.