Precalculus Examples

$\cos (\frac{13 π}{15}) \cos (\frac{π}{30}) + \sin (\frac{13 π}{15}) \sin (\frac{π}{30})$

Step 1

The result can be shown in multiple forms.

Exact Form:

$\cos (\frac{13 π}{15}) \cos (\frac{π}{30}) + \sin (\frac{13 π}{15}) \sin (\frac{π}{30})$

Decimal Form:

$- 0.86602540 \dots$