>>457 の説明

√( (sin(A)-sin(B))^2 +(cos(A)-cos(B))^2)
=√( sin(A)^2+cos(A)^2+sin(B)^2 +cos(B)^2 -2*sin(A)*sin(B)-2*cos(A)*cos(B) )
=√( 2 - 2*sin(A)*sin(B)-2*cos(A)*cos(B) )
=√( 2 - 2*cos(A-B) )

=2*√( ( 1 - cos(A-B) )/2 )
=abs(2*sin( (A-B)/2 ))

つまり(A-B)が小さいならほぼ比例する