Question

If for all real values of $x,\cos \theta =x+\frac{1}{x}$, then

• A. $\theta$ is an acute angle
• B. $\theta$ is right angle
• C. $\theta$ is an obtuse angle
• D. no such $\theta$ exists

Answer 1

Answer: (D)

we know that $x+\frac{1}{x}\ge 2$
$\Rightarrow \cos \theta \ge 2$ not possible