Precalculus Examples

$\cos (\frac{π}{5}) \cos (\frac{2 π}{15}) - \sin (\frac{π}{5}) \sin (\frac{2 π}{15})$

Step 1

The result can be shown in multiple forms.

Exact Form:

$\cos (\frac{π}{5}) \cos (\frac{2 π}{15}) - \sin (\frac{π}{5}) \sin (\frac{2 π}{15})$

Decimal Form:

$0.50000000 \dots$