Evaluate \(\cos leaving the answer in surd form.
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Correct Answer: Option B
Explanation:
\(\cos(a + b) = \cos a\cos b - \sin a\sin = \cos(30 + 45) = (\cos30)(\cos45) - (\sin30)(\sin45)\)
= \((\frac{\sqrt{3}}{2} \times \frac{\sqrt{2}}{2}) - (\frac{1}{2} \times \frac{\sqrt{2}}{2})\)
= \(\frac{\sqrt{6} - \sqrt{2}}{4}\)
= \(\frac{\sqrt{2}(\sqrt{3} - 1)}{4}\)
\(\cos(a + b) = \cos a\cos b - \sin a\sin = \cos(30 + 45) = (\cos30)(\cos45) - (\sin30)(\sin45)\)
= \((\frac{\sqrt{3}}{2} \times \frac{\sqrt{2}}{2}) - (\frac{1}{2} \times \frac{\sqrt{2}}{2})\)
= \(\frac{\sqrt{6} - \sqrt{2}}{4}\)
= \(\frac{\sqrt{2}(\sqrt{3} - 1)}{4}\)