() ().
:
10. ():
.
20. ():
.
11) I.
16. .
l .
( ) l , .
l l .
,
l = | a | cos .
l.
(. 50, ), l 1 1 l.
,
(. 50,), l 1 .
,
l, = 90 l = | a | cos 90 = 0.
.
1. b
l ( + b) = l + lb, l .
.
2. k
l k a = k l a,
l .
.
, .
, l . (. 51).
, (i = e). j k , l.
= OA > , , z. , ,
l = | a | cos .
| a | cos = x, . . l .
( 11), , , l l.
, .