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

Assessment: WAEC SSCE - Further Mathematics - 2010 (Objective) Subject: Further Mathematics

Question 1 Report

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

Answer Details
Using the sum to product formula, we have: \begin{align*} \cos(60° + 45°) &= \cos 60° \cos 45° - \sin 60° \sin 45° \\ &= \frac{1}{2} \cdot \frac{\sqrt{2}}{2} - \frac{\sqrt{3}}{2} \cdot \frac{\sqrt{2}}{2} \\ &= \frac{\sqrt{2} - \sqrt{6}}{4} \end{align*} Therefore, the correct answer is option C: \(\frac{\sqrt{2} - \sqrt{6}}{4}\).

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