(ax+by)^2+(ay-bx)^2=a2x2+2axby+b2y2+a2y2-2aybx+b2x2=(a2x2+a2y2)+(b2y2+b2x2)=a2(x2+y2)+b2(y2+x2)=(a2+b2)(x2+y2)
Тождество доказана
(ax+by)^2+(ay-bx)^2=a2x2+2axby+b2y2+a2y2-2aybx+b2x2=(a2x2+a2y2)+(b2y2+b2x2)=a2(x2+y2)+b2(y2+x2)=(a2+b2)(x2+y2)
Тождество доказана