[tex]\bf 20000\pi \iff 10000\cdot 2\pi \implies cos(2\pi )=1\qquad 10000\cdot 1\implies 1
\\\\\\
sin(2\pi )=0\qquad \qquad 10000\cdot 0\implies 0\\\\
-----------------------------\\\\
cos({{ \alpha}} + {{ \beta}})= cos({{ \alpha}})cos({{ \beta}})- sin({{ \alpha}})sin({{ \beta}})\\\\
-----------------------------\\\\
cos(x+10000\pi )=cos(x)cos(10000\pi )-sin(x)sin(10000\pi )
\\\\\\
cos(x+10000\pi )=cos(x)\cdot 1-sin(x)\cdot 0
\\\\\\
cos(x+10000\pi )=cos(x)[/tex]
