Question:
Evaluate the following integrals:
$\int \frac{2 \cos x-3 \sin x}{6 \cos x+4 \sin x} d x$
Solution:
Taking 2 common in denominator we get
$\Rightarrow \int \frac{2 \cos x-3 \sin x}{2(3 \cos x+2 \sin x)} d x$
Now assume
$3 \cos x+2 \sin x=t$
$(-3 \sin x+2 \cos x) d x=d t$
Put $t$ and dt in given equation we get
$\Rightarrow \frac{1}{2} \int \frac{\mathrm{dt}}{\mathrm{t}}$
$=\frac{1}{2} \ln |\mathrm{t}|+\mathrm{c}$
But $t=3 \cos x+2 \sin x$
$=\frac{1}{2} \ln |3 \cos x+2 \sin x|+c$