Sumas de cuadrados producto

(a^2+b^2) (A^2+B^2) = (aA+bB)^2 + (aB-bA)^2

(a^2+b^2+c^2+d^2) (A^2+B^2+C^2+D^2) = (aA+bB+cC+dD)^2 + (aB-bA+cD-dC)^2 + (aC-bD-cA+dB)^2 + (aD-dA+bC-cB)^2

(a^2+b^2+c^2)(x^2+y^2+^z^2)=(ax+by+cz)^2+(bz-cy)^2+(cx-az)^2+(ay-bx)^2

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