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1⎛<br />
1 1 ⎞ 2<br />
= ⎜ + ⎟=<br />
,<br />
2<br />
2⎝2+ x 2−x⎠<br />
4 − x<br />
x x x<br />
( x) x ( x)<br />
2 cos3<br />
′ = 2 ln 2 ⋅ cos3 + 2 − sin 3 ⋅ 3 ,<br />
1 ⋅tg<br />
x−arcsin<br />
x⋅<br />
1<br />
2<br />
2<br />
⎛arcsin x ⎞<br />
′<br />
1−<br />
x<br />
cos x<br />
⎜ ⎟ =<br />
,<br />
2<br />
⎝ tg x ⎠<br />
tg x<br />
⎛ x ⎞<br />
′ 1 ⎛ x ⎞<br />
′ 2<br />
⎜arctg ⎟ = ⋅ ,<br />
2 ⎜ ⎟ =<br />
2 2<br />
⎝ x+ 2⎠ ⎛ x ⎞ ⎝ x+<br />
2⎠ ( x+ 2)<br />
+ x<br />
1+ ⎜ ⎟<br />
⎝ x + 2 ⎠<br />
2x<br />
2x<br />
2<br />
( arccos<br />
′ ⋅e<br />
e ) =−<br />
4x<br />
.<br />
1−e<br />
×èòà÷åâ³ ðåêîìåíäóºìî çàïèñàòè ïîõ³äíó ôóíêö³¿ ó ÷åðåç<br />
îòðèìàí³ ôîðìóëè ³ çà ôîðìóëîþ (7.6.4).<br />
7.7.8. Ñïî÷àòêó ïðîëîãàðèôìóºìî îáèäâ³ ÷àñòèíè ð³âíîñò³<br />
y = x çà îñíîâîþ ÷èñëà å. Ó ðåçóëüòàò³ îäåðæèìî:<br />
2x<br />
ln y =2x ln x. Ïîò³ì çíàéäåìî ïîõ³äí³ â³ä îáîõ ÷àñòèí<br />
îñòàííüî¿ ð³âíîñò³.<br />
Ïðè öüîìó, çàñòîñîâóþ÷è ëîãàðèôì³÷íó ïîõ³äíó, ìàòèìåìî<br />
= 2(lnx<br />
+ 1)<br />
y′ y<br />
.<br />
Çâ³äêè îòðèìàºìî, ùî<br />
2x<br />
( ) àáî ( )<br />
y′ = 2y lnx+ 1 y′<br />
= 2x lnx+ 1 .<br />
³äçíà÷èìî, ùî ïîõ³äíó äàíî¿ ôóíêö³¿ ìîæíà çíàéòè áåçïîñåðåäíüî,<br />
êîðèñòóþ÷èñü ïðè öüîìó ôîðìóëîþ 8 ³ç òàáëèö³.<br />
− ′ − 5( acos t + bsin t)<br />
′ =− − − =<br />
.<br />
2<br />
7.7.9. y 5( asin t bcos t) ( asin t bcos<br />
t)<br />
( asin<br />
t − bcost)<br />
2<br />
7.7.10.<br />
( sin )′<br />
⎛cos<br />
α⋅tg<br />
α⎞ ′ α cos α<br />
y′ = ⎜ ⎟ = = , c −ñòàëà .<br />
⎝ 1+2tgc ⎠ 1+ 2tgc 1+<br />
2tgc<br />
Ñë³ä ìàòè íà óâàç³, ùî íå çàâæäè äîö³ëüíî äèôåðåíö³þâàòè<br />
çàäàíó ôóíêö³þ â³äðàçó. Ìîæíà ïîïåðåäíüî ï³ääàòè ¿¿<br />
òîòîæí³ì ïåðåòâîðåííÿì, ÿêùî öå âåäå äî ñïðîùåííÿ äèôåðåíö³þâàííÿ.<br />
Òðåáà òàêîæ óÿâëÿòè, ùî ÿê àðãóìåíòè, òàê ³<br />
ôóíêö³¿ ìîæóòü áóòè ïîçíà÷åí³ ð³çíîìàí³òíèìè áóêâàìè,<br />
ïðè öüîìó ïåðø çà âñå òðåáà ÷³òêî âèçíà÷èòè, ÿê³ áóêâè<br />
â³äïîâ³äàþòü çì³ííèì âåëè÷èíàì, à ÿê³ ñòàëèì.<br />
ÂÏÐÀÂÈ<br />
Çíàéòè ïîõ³äí³ òàêèõ ôóíêö³é (ó äåÿêèõ âèïàäêàõ òðåáà<br />
òàêîæ îá÷èñëèòè çíà÷åííÿ ïîõ³äíèõ ó òî÷ö³):<br />
7.1.<br />
x<br />
3<br />
3<br />
2<br />
= + 3 − ; 7.2. 2<br />
y x x<br />
7.3. y ( x a) 2<br />
7.5.<br />
7.7.<br />
7.9.<br />
y = x− x ;<br />
1 1<br />
= − , a = const; 7.4. s = 2<br />
t<br />
+ t<br />
;<br />
z x x<br />
3<br />
3<br />
= 3 − 2 + 4 ; 7.6.<br />
v =<br />
2<br />
x −<br />
x<br />
2<br />
2t<br />
u = ; t + 3<br />
3<br />
+ 3<br />
; 7.8. y = x 2 sin x;<br />
1+ cosϕ<br />
z = ; 7.10. ctg<br />
sin ϕ y=− 3cos t t;<br />
x<br />
7.11. fx ( ) = ;<br />
1 + x<br />
m t<br />
7.12. Ft () = t<br />
+ m<br />
, m — ïàðàìåòð; îá÷èñëèòè<br />
⎛dF<br />
⎞<br />
⎜ ⎟<br />
⎝ dt ⎠ =<br />
t<br />
m<br />
;<br />
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