Answer
$\dfrac{7.6}{3} \sin (3x-4 )+C$
Work Step by Step
Our aim is to solve the integral $\int 7.6 \cos (3x-4 ) \ dx$
Let us consider that $a =3x-4$ and $\dfrac{da}{dx}=3\implies dx=\dfrac{da}{3}$
Now, $\int 7.6 \cos (3x-4 ) \ dx = \int 7.6 \cos a \times \dfrac{da}{3}$
or, $=\dfrac{7.6}{3} \sin a+C$
or, $=\dfrac{7.6}{3} \sin (3x-4 )+C$
