# Sum of cosines

Geometry Level 4

$A=\cos\left(\frac{13\pi}{20}\right) +\cos\left(\frac{21\pi}{20}\right) +\cos\left(\frac{29\pi}{20}\right) +\cos\left(\frac{37\pi}{20}\right)$

Find the value of $$\lfloor 1000A \rfloor$$.


Notation: $$\lfloor \cdot \rfloor$$ denotes the floor function.

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