Question 1141649
{{{ 3 + cos( 2x ) = 3.5 }}}
{{{ cos( 2x ) = 1/2 }}}
The angles whose cosine = {{{ 1/2 }}} are
in the 1st and 4th quadrants.
{{{ arc cos ( 1/2 ) = pi/3 }}}
{{{ arc cos ( 1/2 ) = 5*( pi/3 ) }}}
----------------------------------
{{{ 2x = pi/3 }}}
{{{ x = pi/6 }}}
and
{{{ 2x = 5*( pi/3 ) }}}
{{{ x = 5*( pi/6 ) }}}