Integral cos pangkat 3 2x dx

[tex] \int\ {cos^3 2x} \, dx [/tex]

misal u=2x
maka
[tex] \frac{du}{dx} =2 \\ \frac{du}{2} =dx[/tex] 

[tex]\int\ {cos^3 2x} \, dx \\ = \int\ {cos^3 u} \, \frac{du}{2} \\ = \frac{1}{2}. \frac{1}{4} sin^4 u+c \\ = \frac{1}{8} sin^4 2x +c[/tex]