Mathematics

Problem

In a

\Delta ABC

\tan\frac{A}{2},\ \tan\frac{B}{2},\ \tan\frac{C}{2}

are in H.P., then the value of

\cot\frac{A}{2}\cot\frac{C}{2}

is: (a) 3 (b) 2 (c) 1 (d)

\sqrt{3}