Question 1131928
{{{(b+a)sin(A) = a*cos(expr(1/2)(B+C))}}}
<pre>
This is not true in general because if it were true in general it
would hold true for an equilateral triangle with

a = b = c = 1 and A = B = C = 60°

Substituting:

{{{(1+1)sin("60°") = 1*cos(expr(1/2)("60°"+"60°"))}}} 

{{{(2)(sqrt(3)/2) = 1*cos(expr(1/2)("120°"))}}}

{{{(2)(sqrt(3)/2) = 1*cos("60°")}}} 

{{{(cross(2))(sqrt(3)/cross(2)) = 1*(1/2)}}}

{{{sqrt(3) = 1/2}}}

Which is false.  So since it is false for an equilateral triangle
with all sides 1 and all angles 60°, it is NOT true in general.
If you inadvertently typed it incorrectly, you may tell me in the
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charge as I am a retired mathematics teacher and I do this for fun.

Edwin</pre>