Question 888065
<pre>
{{{tan(theta/2)-sin(theta)}}}{{{""=""}}}{{{"0"}}}

       Use identity {{{sin(2alpha)=2sin(alpha)cos(alpha)}}}
       with {{{alpha=theta/2}}}
                    {{{sin(2*expr(theta/2))=2sin(theta/2)cos(theta/2)}}}
                    {{{sin(theta)=2sin(theta/2)cos(theta/2)}}}

{{{tan(theta/2)-sin(theta)}}}{{{""=""}}}{{{"0"}}} 

{{{tan(theta/2)-2sin(theta/2)cos(theta/2)}}}{{{""=""}}}{{{"0"}}}

{{{sin(theta/2)/cos(theta/2)-2sin(theta/2)cos(theta/2)}}}{{{""=""}}}{{{"0"}}}

Multiply through by {{{cos(theta/2)}}}

{{{sin(theta/2)-2sin(theta/2)cos^2(theta/2)}}}{{{""=""}}}{{{"0"}}}

Factor out {{{sin(theta/2)}}}

{{{sin(theta/2)(1-2cos^2(theta/2))}}}{{{""=""}}}{{{"0"}}}

{{{sin(theta/2)}}}{{{""=""}}}{{{"0"}}};  {{{1-2cos^2(theta/2)}}}{{{""=""}}}{{{"0"}}}

{{{theta/2}}}{{{""=""}}}{{{"0"}}};  {{{-2cos^2(theta/2)}}}{{{""=""}}}{{{-1}}}

{{{theta}}}{{{""=""}}}{{{"0"}}};  {{{cos^2(theta/2)}}}{{{""=""}}}{{{1/2}}}
                                  
          {{{cos(theta/2)}}}{{{""=""}}}{{{"" +- sqrt(1/2)}}}
          {{{cos(theta/2)}}}{{{""=""}}}{{{"" +- sqrt(2)/2}}}
          {{{theta/2}}}{{{""=""}}}{{{matrix(1,3,pi/4,",",3pi/4)}}}
          {{{theta}}}{{{""=""}}}{{{matrix(1,3,pi/2,",",3pi/2)}}}

Edwin</pre>