Question 896488
<pre>
{{{"tan"^(-1)}}}{{{( sin(A)/(1+cos(A)) )=A/2}}}

{{{matrix(1,2,Let,A = 2B)}}}

{{{"tan"^(-1)}}}{{{( sin(2B)/(1+cos(2B)) )=2B/2}}}

{{{"tan"^(-1)}}}{{{( sin(2B)/(1+cos(2B)) )=B}}}

{{{"tan"^(-1)}}}{{{(   2sin(B)cos(B)    /(1+(2cos^2(B)-1)) )=B}}}

{{{"tan"^(-1)}}}{{{(   2sin(B)cos(B)    /(2cos^2(B)) )=B}}}

{{{"tan"^(-1)}}}{{{(   cross(2)sin(B)cross(cos(B))    /(cross(2)cos^cross(2)(B)) )=B}}}

{{{"tan"^(-1)}}}{{{(   sin(B)/cos(B) )=B}}}

{{{"tan"^(-1)}}}{{{(tan(B[""]))=B}}}

{{{B=B}}}

Edwin</pre>