Straight Lines
Grade 11

Question:

<p>In triangle ABC, if cos&nbsp;<span class="math-tex">\(\frac{A}{2}=\frac{1}{2} \sqrt{\frac{b}{c}+\frac{c}{b}}\)</span>, then :<br /> [Note : All symbols used have usual meaning in triangle ABC]</p>
<p style="display:inline">bc = a<sup>2</sup></p>
<p style="display:inline">ab = c<sup>2</sup></p>
<p style="display:inline">2bc = a<sup>2</sup></p>
<p style="display:inline">2ac = b<sup>2</sup></p>

Step-by-Step Solution

Key Concept: Use the half-angle formula to convert the expression to cos A and then apply the Law of Cosines to find the relation between sides.
<p>2bc = a<sup>2</sup></p>
Correct Answer: C

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