Trigonometry Examples

$\cos (\frac{3}{5}) \cos (\frac{\sqrt{21}}{5}) - \sin (\frac{4}{5}) \sin (\frac{2}{5})$

Step 1

The result can be shown in multiple forms.

Exact Form:

$\cos (\frac{3}{5}) \cos (\frac{\sqrt{21}}{5}) - \sin (\frac{4}{5}) \sin (\frac{2}{5})$

Decimal Form:

$0.22293858 \dots$