Precalculus Examples

$\cos (\frac{5 π}{18}) \cos (\frac{π}{9}) + \sin (\frac{5 π}{18}) \sin (\frac{π}{9})$

Step 1

The result can be shown in multiple forms.

Exact Form:

$\cos (\frac{5 π}{18}) \cos (\frac{π}{9}) + \sin (\frac{5 π}{18}) \sin (\frac{π}{9})$

Decimal Form:

$0.86602540 \dots$