# MTH 251 Lecture Notes - Lecture 36: Cartesian Coordinate System

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15 May 2018

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Section Polar coordinates

Consider a point in the plane.

We call this point the pole (or the origin) and label it

We draw a ray extending from in any direction (but is usually drawn extending rightward).

We call this the polar axis .

If is any other point in the plane, we let be the distance from and we let be the

angle (usually in radians) between the polar axis and the line

The point is represented by where are the polar coordinates of

We continue the convention that an angle in the counter-clock wise direction is positive, and

negative in the clockwise direction.

Polar axis

Polar axis

Polar axis