We show the sine in the unit circle. The unit circle is a circle with radius .

The hypotenuse of the triangle in the unit circle has a length of 1. In this case sine is equal to the opposite:

The sine function is the length of the opposite with regards to the angle . One can easily observe that:

(1)

This is the plot of the sine function between 0 and :

Here are some values of the sine functions that are worth remembering:

Alpha in degree | Alpha in radians | Value of sine of alpha |
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