Thread: Rectangular to polar coordinate conversion

Rectangular coordinates: (0,-6)

Show me how to find the polar coordinates for this please.

Well you have not moved across at all, and gone down 6 units. Surely you can read off what the magnitude is. As for the angle, if you started from the positive x axis and went anticlockwise, what angle is swept out?

Originally Posted by Prove It

Well you have not moved across at all, and gone down 6 units. Surely you can read off what the magnitude is. As for the angle, if you started from the positive x axis and went anticlockwise, what angle is swept out?

Here's what is giving me trouble:

tan(theta) = y/x

Therefore, theta = arctan(y/x)

Plugging in x and y, we get

theta = arctan(-6/0)

Negative six over zero is undefined...so now what?

Originally Posted by TWN

Here's what is giving me trouble:

tan(theta) = y/x

Therefore, theta = arctan(y/x)

Plugging in x and y, we get

theta = arctan(-6/0)

Negative six over zero is undefined...so now what?

Don't apply a formula if you don't understand what it means. Draw a diagram. Surely you can read off your answers from the diagram, if you try it...

Originally Posted by Prove It

Don't apply a formula if you don't understand what it means. Draw a diagram. Surely you can read off your answers from the diagram, if you try it...

Would theta be -pi/2 ? Or -3pi/2 ? Or am I still not looking at it right?

It's either if you move anticlockwise, or if you move clockwise. Generally we define , so choose .

Now what is r?

Would it be 6 or -6?

r represents the magnitude, magnitudes can never be negative.