Solve the Equation for Exact Solutions $\arccos x + \arccos 2 x = \arccos \frac { 1 } { 2 }$

Multiple Choice

Solve the equation for exact solutions.
- $\arccos x + \arccos 2 x = \arccos \frac { 1 } { 2 }$

A) $\{ 2 \}$
B) $\left\{ - \frac { 3 } { 4 } , \frac { 3 } { 4 } \right\}$
C) $\{ - 5 + 3 \sqrt { 2 } \}$
D) $\left\{ \frac { 1 } { 2 } \right\}$