Cos180°=-1
cos90°=0
cos360°=1
cos180°=-1
Otvet:2, α=90°
1.1 = {0; 2; 1}
1.2 = {4; 9; 1}
1.3 = {16; 4; 1}
1.4 = {2; -2; -1} * {6; 5;2} = {12; -10; -2}
2. a={-2; 3}
7. 6i+g-k
10. a={1.5; -2; 6}
12. {9; 0; 3}
2.7х-15.6=1.248:0.1
2.7х-15.6=12.48
2.7х=12.48+15.6
2.7х=28.08
х=28.08:2.7
х=10.4
Ответ: х=10.4