Unit Circle


A unit circle is a circle with the radius of 1. A unit circle has radians, degrees, and coordinates.

Sample Problem

In the interval 0<=x<360, when is cot x is undefined?


It is 0 and 180.
-In a unit circle, 0 and 360 degrees has the coordinate of (1,0); 90 degrees has the coordinate of (0,1); 180 degrees has the coordinate of (-1,0); 270 degrees has the coordinate of (0,1).
-The denominator must be zero and any number that is not zero in the numerator can have the answer to be undefined.
-Tan x is sin x/cos x.
-Cot x is the co-function of tan x, so it is 1/sin x/cos x or cos x/sin x.

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