Sums of three squares = sum of three squares
If t1 = a1*d1 + a2*d2 - b1*c1 - b2*c2; s1 = a1*d1 - a2*d2 - b1*c1 + b2*c2; t2 = a1*b2 + c1*a2 + b1*d2 + d1*c2; s2 = a1*b2 - c1*a2 + b1*d2 - d1*c2; t3 = a1*a2 + c1*b2 + b1*c2 + d1*d2; s3 = a1*a2 - c1*b2 + b1*c2 - d1*d2; then t1*t1 + t2*t2 + s3*s3 = s1*s1 + s2*s2 + t3*t3 Illustration: Set t1 = 3*19 +... Sign in to see full entry.