Question

If $\sum _{i=1}^{10}{\cos }^{-1}{x}_i=0$ then $\sum _{i=1}^{10}{x}_i$ is

• A. 0
• B. 10
• C. 5
• D. none of these

Answer 1

The correct option is B 10

Given $\sum _{i=1}^{10}{\cos }^{-1}{x}_i=0$

As ${\cos }^{-1}{x}_i\ge 0$

So the only option is ${\cos }^{-1}{x}_i=0⟹x_i=1$

$\sum _{i=1}^{10}{x}_i=\sum _{i=1}^{10}1=1\times 10=10$