Question

If in $\Delta ABC$, $AC$ is double of $AB$, then the value of $\cot \frac{A}{2}.\cot \frac{B-C}{2}$ is equal to

• A. $\frac{1}{3}$
• B. $-\frac{1}{3}$
• C. 3
• D. $\frac{1}{2}$

Answer 1

The correct option is C 3

Given $b=2c$
$\therefore \cot \frac{A}{2}.\cot \frac{B-C}{2}=\frac{b+c}{b-c}=\frac{2c+c}{2c-c}=3$ using above formula.