AB→ = В - A = 3−0;−5−(−4)3 - 0; -5 - (-4)3−0;−5−(−4) = 3;−13; -13;−1 BC→ = C - B = 1−3;−3−(−5)1 - 3; -3 - (-5)1−3;−3−(−5) = −2;2-2; 2−2;2 CA→ = A - C = 0−1;−4−(−3)0 - 1; -4 - (-3)0−1;−4−(−3) = −1;−1-1; -1−1;−1
AB→⋅BC→ = 3−2-2−2 + −1-1−12 = -6 - 2 = -8AB→⋅CA→ = 3−1-1−1 + −1-1−1−1-1−1 = -3 + 1 = -2
AB→⋅BC→ + AB→⋅CA→ = -8 + −2-2−2 = -10
Ответ: -10.
AB→ = В - A = 3−0;−5−(−4)3 - 0; -5 - (-4)3−0;−5−(−4) = 3;−13; -13;−1 BC→ = C - B = 1−3;−3−(−5)1 - 3; -3 - (-5)1−3;−3−(−5) = −2;2-2; 2−2;2 CA→ = A - C = 0−1;−4−(−3)0 - 1; -4 - (-3)0−1;−4−(−3) = −1;−1-1; -1−1;−1
AB→⋅BC→ = 3−2-2−2 + −1-1−12 = -6 - 2 = -8
AB→⋅CA→ = 3−1-1−1 + −1-1−1−1-1−1 = -3 + 1 = -2
AB→⋅BC→ + AB→⋅CA→ = -8 + −2-2−2 = -10
Ответ: -10.