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dy<br />
dx = lim<br />
D ®<br />
f(u + Du) − f(u)<br />
. lim<br />
Du D ®<br />
Persamaan 5.12 disebut aturan rantai<br />
Du<br />
Dx = dy du<br />
dx dx (terbukti)<br />
Contoh 5.7<br />
dy<br />
Tentukan jika y = (4x 3 + 5x 2 – x + 4) 3<br />
dx<br />
Penyelesaian :<br />
Misal u = 4x 3 + 5x 2 – x + 4 y = u 3<br />
du<br />
dx = 12x + 10x − 1 dy<br />
du = 3u<br />
dy<br />
dx = dy du<br />
= 3u (12x + 10x − 1)<br />
du dx<br />
= 3(12x + 10x − 1)(4x + 5x − x + 4)<br />
Soal-soal<br />
Tentukan turunan pertama dari fungsi-fungsi berikut!<br />
1. f(t) = at − bt + 7 6. f(x) = 5 4x<br />
− √3x<br />
4x 5 + 1 x<br />
3<br />
2. f(x) = 3x + 5x<br />
3. g(x) = 2 x + x 2<br />
4. h(x) = 4x<br />
5 + 1 x<br />
7. g(t) = (at + bt + c) (3at − 7)<br />
8. h(w) = b − aw<br />
w + c<br />
(at − bt)<br />
9. v(t) =<br />
(ct − d)<br />
5. w(x) = 7 (2t + 3)<br />
− √2x + 3 10. g(t) = t<br />
4x t − 3<br />
5.6 Turunan fungsi-fungsi trigonometri<br />
y = f(x) = sin x , maka dy = f'(x) = cos x (5.13)<br />
dx<br />
Bukti<br />
dy<br />
= f'(x) = lim<br />
dx D ®<br />
= lim<br />
D ®<br />
= lim<br />
D ®<br />
f(x + Dx) − f(x)<br />
Dx<br />
= lim<br />
D ®<br />
sin x cos Dx + cos x sinDx − sin x<br />
Dx<br />
sin x (cos Dx − 1) + cos x sinDx<br />
Dx<br />
sin(x + Dx) − sin x<br />
Dx<br />
= lim<br />
D ®<br />
(cos Dx − 1) sin Dx<br />
sin x + cos x<br />
Dx<br />
Dx<br />
101