Expand Using Sum/Difference Formulas cos((5pi)/7)cos((5pi)/42)-sin((5pi)/7)sin((5pi)/42)

$\cos (\frac{5 π}{7}) \cos (\frac{5 π}{42}) - \sin (\frac{5 π}{7}) \sin (\frac{5 π}{42})$

Step 1

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$\cos (\frac{5 π}{7}) \cos (\frac{5 π}{42}) - \sin (\frac{5 π}{7}) \sin (\frac{5 π}{42})$