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4.5. ÏÎÍßÒÒß ÏÐΠвÂÍßÍÍß ÏËÎÙÈÍÈ<br />
² ÏÐßÌί Ó ÏÐÎÑÒÎв<br />
4.5.1. Çàãàëüíå ð³âíÿííÿ ïëîùèíè<br />
Íåõàé ïëîùèíà Ð ïðîõîäèòü ÷åðåç òî÷êó M 0 (x 0 , y 0 , z 0 )<br />
r<br />
³ ïåðïåíäèêóëÿðíà âåêòîðó n=<br />
( A, B,<br />
C)<br />
(ðèñ. 4.26).<br />
Îòðèìàíå ð³âíÿííÿ ïëîùèíè çîáðàçèìî ó âèãëÿä³:<br />
( ) ( ) ( )<br />
Ax- x + By- y + Cz- z =<br />
0 0 0<br />
0<br />
àáî<br />
Ax + By + Cz + D = 0 , (4.5.2)<br />
äå D Ax0 By0 Cz0<br />
=- - - .<br />
Îçíà÷åííÿ 4.5.1. гâíÿííÿ (4.5.2) íàçèâàºòüñÿ çàãàëüíèì<br />
ð³âíÿííÿì ïëîùèíè.<br />
Ìîæíà ïîêàçàòè, ùî áóäü-ÿêå ð³âíÿííÿ ïåðøîãî ñòåïåíÿ<br />
2 2 2<br />
ç òðüîìà çì³ííèìè çà óìîâè, ùî A + B + C ¹ 0 , º ð³âíÿííÿ<br />
ïëîùèíè.<br />
Äåÿê³ ñòàë³ À,  ³ Ñ ìîæóòü áóòè ð³âíèìè íóëþ, àëå íå<br />
âñ³ çðàçó. Ïðè öüîìó ñòàëà D ìîæå áóòè ÿêîþ çàâãîäíî.<br />
Çîêðåìà, ÿêùî D = 0, òî ïëîùèíà, ÿêà â³äïîâ³äຠð³âíÿííþ<br />
(4.5.2), ïðîõîäèòü ÷åðåç ïî÷àòîê êîîðäèíàò.<br />
Òåïåð íåõàé À =  = D = 0, à C ≠ 0, òîä³ ð³âíÿííÿ (4.5.2)<br />
áóäå ìàòè äóæå ïðîñòèé âèä z = 0. Öå ð³âíÿííÿ âèçíà÷àº<br />
êîîðäèíàòíó ïëîùèíó Îxy.  ³íøèõ îêðåìèõ âèïàäêàõ<br />
ïðîïîíóºìî ÷èòà÷åâ³ ðîç³áðàòèñÿ ñàìîñò³éíî.<br />
Äâ³ ïëîùèíè â ïðîñòîð³ ìîæóòü áóòè ïàðàëåëüíèìè òà<br />
ïåðïåíäèêóëÿðíèìè. Íåõàé â³äïîâ³äíî çàäàíî äâ³ ïëîùèíè<br />
ñâî¿ìè ð³âíÿííÿìè<br />
Ðèñ. 4.26<br />
Ö³ºþ óìîâîþ âèçíà÷àºòüñÿ ºäèíà ïëîùèíà â ïðîñòîð³<br />
Oxyz. Ïðè öüîìó âåêòîð n r<br />
íàçèâàºòüñÿ íîðìàëüíèì âåêòîðîì<br />
ïëîùèíè Ð. ³çüìåìî íà ïëîùèí³ Ð äîâ³ëüíó òî÷êó<br />
M(x, y, z).<br />
uuuuur<br />
Òîä³ âåêòîð MM<br />
0<br />
= ( x-x0, y- y0,<br />
z-z0)<br />
áóäå ïåðïåíäèêóëÿðíèé<br />
âåêòîðó n=<br />
( A, B,<br />
C)<br />
. Îòæå, ñêàëÿðíèé äîáóòîê öèõ<br />
r<br />
âåêòîð³â äîð³âíþº íóëþ, òîáòî<br />
v uuuuur<br />
nMM × 0<br />
= 0 . (4.5.1)<br />
Ax<br />
1<br />
+ By<br />
1<br />
+ Cz<br />
1<br />
+ D1 = 0 , (4.5.3)<br />
Ax<br />
2<br />
+ By<br />
2<br />
+ Cz<br />
2<br />
+ D2 = 0. (4.5.4)<br />
Ìîæíà ïîêàçàòè, ùî óìîâîþ ïàðàëåëüíîñò³ äâîõ ïëîùèí<br />
º ïðîïîðö³îíàëüí³ñòü êîåô³ö³ºíò³â ïðè îäíîéìåííèõ çì³ííèõ<br />
A1 B1 C1<br />
= = ,<br />
A B C<br />
(4.5.5)<br />
2 2 2<br />
à óìîâîþ ¿õ ïåðïåíäèêóëÿðíîñò³:<br />
AA<br />
1 2<br />
+ BB<br />
1 2<br />
+ CC<br />
1 2<br />
= 0<br />
(4.5.6)<br />
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