Posted by andi telaumbanua on Feb 13, 2018 in
Matematika |
Tentukan turunan pertama dari y = cos^4 (4x^2- x) !
Jawab:
Gunakan aturan rantai
Misalkan: a = (4x^2- x)
maka: da/dx=8x-1
Misalkan: b = cos a
maka: db/da=-sina = -sin(4x^2- x)
Sehingga: y = b^4
maka: dy/db=4b^3 = 4(cos a)^3 = 4[cos(4x^2- x)]^3
Maka: dy/db=4 cos^3 (4x^2- x)
Sehingga:
dy/dx = (dy/db)(db/da)(da/dx)
dy/dx = (4 cos^3 (4x^2- x) )(-sin(4x^2- x) )(8x-1)
dy/dx = [8x-1] [-4cos^3 (4x^2- x) sin(4x^2- x)]
dy/dx = [-32x cos^3 (4x^2- x) sin(4x^2- x)] – [-4〖cos〗^3 (4x^2- x) sin(4x^2- x)]
dy/dx = 4cos^3 (4x^2- x) sin(4x^2- x) – 32x cos^3 (4x^2- x) sin(4x^2- x)