x^2+xy+y^2>(x+y/2)^2
y^2+yz+z^2>(y/2+z)^2
√(x^2+xy+y^2)>x+y/2
√(y^2+yz+z^2)>y/2+z
√(x^2+xy+y^2)+√(y^2+yz+z^2)>x+y+z