Question

The multiplication inverse of a number is the number itself, then its initial value is.

• A. i
• B. – 1
• C. 2
• D. – i

Answer 1

Answer: (B)

– 1

Answer 2

We know that, multiplicative inverse of $= \frac{2i\sin\theta}{2(1 - \cos\theta)}$ is $= \frac{i.2\sin\frac{\theta}{2}\cos\frac{\theta}{2}}{2\sin^{2}\frac{\theta}{2}}$ According to question $= i\frac{\cos\frac{\theta}{2}}{\sin\frac{\theta}{2}} = i\cot\frac{\theta}{2}$ and only (2) is satisfying such condition.