Cos is the short version of the trigonometry Cosine() function.
This short version is always used in equations and expressions since it takes less space.
Used in an equation it might look like
cos x = -0.22
This would be interpreted as "The cosine of x is -0.22". Most mathematicians would speak it as
"cosine x equals negative 0.22". (It is sometimes spoken as 'cos' also).
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