1)АВ{1;1;-2}, CD{-2;-2;4}
Cosα = ( -2-2+8)/√(1 +1 +4)*√(4 +4 +16) = 4/√6*√24 = 4/12 = 1/3
α = arcCos1/3
2) a) Cosα = (56 +0 +22)/√(64 +9 +121)*√(49 +0 +4) = 78/√194*√54= 78/√10476≈
≈0,78
α≈arcCos0,78
b) Cosα = (8 +4,5+24,5)/√16+9+49)*√4+2,25+12,25) = 36/37
α= arcCos36/37
с)Cos α=(-4/7-7 -28)/√(4/9+49/81+4)*√(4 +81 +196) ≈ -35 4/7 / 339≈ -0,6
α ≈ arcCos(-0,6)
d) Cosα = (0,45 + 9,8+135,2)/√(0,09+1,96+27,04)*√(2,25+49+676)≈
≈0,2
α≈arcCos0,2