Algebraic measure of the orthogonal projection on one of the sides of an angle of measure θ of a unit vector carried by the other side of the angle.
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\(\cos{(\textit{θ})}\space = \space \frac{x}{1}\space = \space x\)
When we associate with any real number the cosine of the angle whose measure, in the circular system, is this number, we thereby define a circular function called a cosine function.
Notation
The cosine of the angle x is noted as cos(x) and is read as “cos of x” or “cosine of angle x“.
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