What is the Negative of a Polar Coordinate?

In summary, negative polar coordinates are a type of coordinate system that uses a distance and angle from a fixed point to represent points in a two-dimensional plane. The negative sign indicates that the point is located in the opposite direction from the origin. They differ from positive polar coordinates in that the angle θ is measured clockwise from the negative x-axis. This allows for representation of points in all four quadrants. To convert to Cartesian coordinates, we use x = -r cos(θ) and y = -r sin(θ). Negative polar coordinates are commonly used in physics, engineering, navigation, and other fields where direction and distance are important. They are also used in analyzing circular or rotational motion and in polarized light microscopy and mapping systems.
  • #1
Physicist3
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Hi,

Say I have a variable 'x' which has the polar value 10@-75°, would '-x' be -10@+75° or 10@+75° as I am a touch confused as to which bit I have to invert
 
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  • #2
Physicist3 said:
Hi,

Say I have a variable 'x' which has the polar value 10@-75°, would '-x' be -10@+75° or 10@+75° as I am a touch confused as to which bit I have to invert
The notation "-x" usually refers to the additive inverse of x. That is, we want x + (-x) = 0. Therefore, if you are using the usual Euclidean notion of vector addition (the parallelogram law, equivalent to the addition of Cartesian components), you must find the polar components of the vector whose addition to x will yield the additive identity: the 0 vector. In the vectors of Euclidean geometry, this is the vector that points in opposite direction to x, but with equal magnitude. Thus, it is the reflection of x through the origin (if one attaches the tail of x to the origin). Attached is an example of the geometric viewpoint. Do you see which vector that should be for your particular case ? After you find it geometrically, then you would find its polar components.
Of course, if you are using a different notion of vector addition, then your result will vary. In that case, you would have to describe the context of your application.
 

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  • #3
Physicist3 said:
Hi,

Say I have a variable 'x' which has the polar value 10@-75°, would '-x' be -10@+75° or 10@+75° as I am a touch confused as to which bit I have to invert
In polar coordinates x and -x have the same magnitude and have angles which differ by 180 deg. In your example -x is 10@105 deg.
 

Related to What is the Negative of a Polar Coordinate?

1. What are negative polar coordinates?

Negative polar coordinates are a type of coordinate system used in mathematics and science to represent points in a two-dimensional plane. They consist of a distance (r) and an angle (θ) from a fixed point, usually the origin. The negative sign indicates that the point is located in the opposite direction from the origin.

2. How are negative polar coordinates different from positive polar coordinates?

Negative polar coordinates differ from positive polar coordinates in that they represent points in the opposite direction from the origin. In positive polar coordinates, the angle θ is measured counterclockwise from the positive x-axis, while in negative polar coordinates, it is measured clockwise from the negative x-axis.

3. What is the significance of the negative sign in negative polar coordinates?

The negative sign in negative polar coordinates indicates that the point is located in the opposite direction from the origin. This is important because it allows us to represent points in all four quadrants of a Cartesian plane, rather than just the first quadrant as in positive polar coordinates.

4. How do you convert negative polar coordinates to Cartesian coordinates?

To convert negative polar coordinates to Cartesian coordinates, we use the following formulas:
x = -r cos(θ)
y = -r sin(θ)
where r is the distance from the origin and θ is the angle measured clockwise from the negative x-axis. These formulas can be derived from the Pythagorean theorem and trigonometric identities.

5. What are some real-world applications of negative polar coordinates?

Negative polar coordinates are commonly used in physics, engineering, and navigation. They are particularly useful in situations where direction and distance are important, such as in calculating the position of satellites or aircraft. They are also used in analyzing the motion of objects in circular or rotational motion, such as planets orbiting the sun. Additionally, negative polar coordinates are used in polarized light microscopy and in coordinate systems for mapping the Earth's surface.

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