Question 985633


Let  {{{alpha}}} = {{{arccos(x)}}}  and  {{{beta}}} = {{{arccos(x/2)}}}.


Then  {{{cos(alpha)}}} = {{{x}}}  and  {{{cos(beta)}}} = {{{x/2}}}. 


Since  {{{alpha}}} = {{{beta}}}  by the condition,  it implies that 


{{{x}}} = {{{x/2}}}.


It is possible only if   {{{x}}} = {{{0}}}.


<B>Answer</B>. &nbsp;x = 0.