cis is often used by mathematicians as a shorthand as

cis(x) = cos(x) + i*sin(x)

This function is often used when speaking of vectors in a 2-dimensional plane representing the set of complex numbers. In this use (keeping with the example above) x represents the angle a unit vector makes with the positive real axis and cis(x) its complex representation.

Perhaps one of its most famous uses is in Euler's formula, relating the exponentiation function to the trigonometric functions.

The Commonwealth of Independent States, a loose economic and political (sort of) union among 11 of the 15 republics that made up the USSR

Members:

The Baltic Republics and Georgia declined to join the CIS, the Baltics states with good reason (they just fought to get out of one union, why join another?). Later, however, Georgia reconsidered and joined the CIS.

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