What are the polar coordinates of (1,-2) and how do you find them?

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Homework Help Overview

The discussion revolves around converting Cartesian coordinates (1, -2) into polar coordinates, focusing on finding representations with different values of r and ensuring the angle theta falls within the specified range of 0 to 2π.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the use of the tangent function and the relationship between Cartesian and polar coordinates. There is an exploration of the angle theta derived from arctan and its validity within the specified range.

Discussion Status

Participants are actively questioning the validity of the calculated angle theta and its placement within the required interval. There is an acknowledgment of the need to adjust the angle to fit the specified range, indicating a productive exploration of the problem.

Contextual Notes

There is uncertainty regarding the calculation of arctan and its conversion to the appropriate angle within the specified range. Participants are also navigating the implications of negative angles and their adjustments.

Jbreezy
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Homework Statement



Convert (1,-2) to polar coordinates find one representation with r >0 and one with r <0. Also 0<= theta <= 2 PI

Homework Equations



I used tantheta = y /x , and x^2 +y^2 = r^2

The Attempt at a Solution



I got (sqrt(5) , arctan(-2)) , (-sqrt(5) , arctan(-2) + pi )
Is this OK?
 
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Does arctan(-2) satisfy 0 <= theta <= 2 pi?
 
I think so it is -63.43 degrees in my calculator and I forget how arctan comes back in the calculator but if I add 180 to that it is still only 116. I forget where is comes back to the domain on the calculator I mean.
 
But -63.43° is not in the interval [0°, 360°]. That was essentially what SteamKing was objecting to.
 
OH opps. OK so add 360 to it. Then I'm good right?
 

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