Question

If $\tan^{-1}(x) + \tan^{-1}(y) + \tan^{-1}(z) = \frac{\pi}{2}$, then $xy + yz + zx =$

• A. 0
• B. 1
• C. -1
• D. $xyz$

Hint:

If $\sum \tan^{-1}x = \pi/2$, then $\sum xy = 1$. If $\sum \tan^{-1}x = \pi$, then $\sum x = xyz$.

Answer 1

The Correct Option is B