a+b=c
a^2+b^2+2ab=c^2 a^2+b^2-c^2=-2ab
a-c=b
a^2-2ac+c^2=b^2 a^2+c^2-b^2=2ac
b-c=a
b^2-2bc+c^2=a^2 b^2+c^2-a^2=2bc
b^2+c^2-a^2/2bc+(c^2+a^2-b^2/2ca)+(a^2+b^2-c^2/2ab)
=1+1-1=1
a+b=c
a^2+b^2+2ab=c^2 a^2+b^2-c^2=-2ab
a-c=b
a^2-2ac+c^2=b^2 a^2+c^2-b^2=2ac
b-c=a
b^2-2bc+c^2=a^2 b^2+c^2-a^2=2bc
b^2+c^2-a^2/2bc+(c^2+a^2-b^2/2ca)+(a^2+b^2-c^2/2ab)
=1+1-1=1