Expand Using Sum/Difference Formulas cos((19pi)/42)cos((2pi)/7)+sin((19pi)/42)sin((2pi)/7)

$\cos (\frac{19 π}{42}) \cos (\frac{2 π}{7}) + \sin (\frac{19 π}{42}) \sin (\frac{2 π}{7})$

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$\cos (\frac{19 π}{42}) \cos (\frac{2 π}{7}) + \sin (\frac{19 π}{42}) \sin (\frac{2 π}{7})$