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Given $$\cos(A - B) = \cos A \cos B + \sin A \sin B$$, the value of $$\cos 15^\circ =$$ _______________
Correct Answer: 0.966
$$\cos 15^\circ = \cos(45^\circ - 30^\circ) = \cos 45^\circ \cos 30^\circ + \sin 45^\circ \sin 30^\circ = \frac{1}{\sqrt{2}} \cdot \frac{\sqrt{3}}{2} + \frac{1}{\sqrt{2}} \cdot \frac{1}{2} = \frac{\sqrt{3} + 1}{2\sqrt{2}} \approx 0.966$$.
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