Question

The value of $\cot \left({\cot }^{-1}(-1)+{\cot }^{-1}(-2)+{\cot }^{-1}(-3)\right)$ equals

• A. 0
• B. $\frac{1}{\sqrt{2}}$
• C. $\frac{1}{3}$
• D. not defined

Answer 1

Answer: (A)

$\cot \left({\cot }^{-1}(-1)+{\cot }^{-1}(-2)+{\cot }^{-1}(-3)\right)=\cot \left(3\pi -\frac{\pi }{2}\right)=\cot \frac{5\pi }{2}=0$