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Find the value of \cos(60° + 45°) leaving your a...

Find the value of \cos(60° + 45°) leaving your answer in surd form

A.

\frac{6 + \sqrt{2}}{4}

B.

\frac{3 + \sqrt{6}}{4}

C.

\frac{\sqrt{2} - \sqrt{6}}{4}

D.

\frac{3 - \sqrt{6}}{4}

Correct answer is C

\cos (x + y) = \cos x \cos y - \sin x \sin y

\cos (60 + 45) = \cos 60 \cos 45 - \sin 60 \sin 45

= \frac{1}{2} \times \frac{\sqrt{2}}{2} - \frac{\sqrt{3}}{2} \times \frac{\sqrt{2}}{2}

= \frac{\sqrt{2} - \sqrt{6}}{4}