Trigonometry Examples

$\cos (\frac{3 π}{7}) \cos (\frac{2 π}{21}) + \sin (\frac{3 π}{7}) \sin (\frac{2 π}{21})$

Step 1

The result can be shown in multiple forms.

Exact Form:

$\cos (\frac{3 π}{7}) \cos (\frac{2 π}{21}) + \sin (\frac{3 π}{7}) \sin (\frac{2 π}{21})$

Decimal Form:

$0.5$