
595
594
ÎÑÍÎÂÍÛÅ ÔÎÐÌÓËÛ Ãåîìåòðèÿ
Ñâîéñòâà âåêòîðíîãî ïðîèçâåäåíèÿ (
cba ,,
ëþáûå âåêòîðû,
l
ëþáîå ÷èñëî):
1
0
.
,abba ´-=´
ò. å. ïðè ïåðåìåíå ìåñò ñîìíî-
æèòåëåé âåêòîðíîå ïðîèçâåäåíèå ìåíÿåò çíàê.
2
0
.
cbcacba ´+´=´+ )(
(ðàñïðåäåëèòåëüíûé
çàêîí).
3
0
.
baba ´l=´l
(ñî÷åòàòåëüíûé çàêîí).
Îïðåäåëåíèå ñìåøàííîãî ïðîèçâåäåíèÿ âåêòîðîâ
cba ,,
:
.
cbacbacba ´=´=
Ôîðìóëà äëÿ âû÷èñëåíèÿ ñìåøàííîãî ïðîèçâå-
äåíèÿ âåêòîðîâ
},;;{
111
ZYXa
};;{
222
ZYXb
è
:
;;
333
ZYXc
.
333
222
111
ZYX
ZYX
ZYX
cba =
Ñâîéñòâà ñìåøàííîãî ïðîèçâåäåíèÿ (
dcba ,,,
ëþáûå âåêòîðû,
l
ëþáîå ÷èñëî):
1
0
.
),()()( bcaabccabbacacbcba -=-=-===
ò. å. ñìåøàííîå ïðîèçâåäåíèå íå ìåíÿåòñÿ ïðè êðó-
ãîâîé ïåðåñòàíîâêå ñîìíîæèòåëåé è ìåíÿåò çíàê ïðè
ïåðåñòàíîâêå äâóõ ñîìíîæèòåëåé.
2
0
.
dcbdcadcba +=+
(ðàñïðåäåëèòåëüíûé
çàêîí).
3
0
.
cbacba l=l
(ñî÷åòàòåëüíûé çàêîí îòíî-
ñèòåëüíî ñêàëÿðíîãî ìíîæèòåëÿ).
20. Ïðèçìà è ïðîèçâîëüíûé ïàðàëëåëåïèïåä
Îáîçíà÷åíèÿ:
l
áîêîâîå ðåáðî;
h
âûñîòà;
P
ïåðèìåòð îñíîâàíèÿ;
S
ïëîùàäü îñíîâàíèÿ;
Ð
ñå÷
ïåðèìåòð ïåðïåíäèêóëÿðíîãî ñå÷åíèÿ
A
0
B
0
C
0
D
0
;
S
ñå÷
ïëîùàäü ïåðïåíäèêóëÿðíîãî ñå÷åíèÿ
A
0
B
0
C
0
D
0
;
S
áîê
ïëîùàäü áîêîâîé ïîâåðõíîñòè;
V
îáúåì.
Îáúåì ïðîèçâîëüíîé ïðèçìû (ðèñ. 342):
== VShV ;
S
ñå÷
l.
Áîêîâàÿ ïîâåðõíîñòü ïðîèçâîëüíîé ïðèçìû
(ðèñ. 342):
S
áîê
= P
ñå÷
l.