Question
Find: $\int \frac{(3 \sin \phi-2) \cos \phi}{5-\cos ^{2} \phi-4 \sin \phi} d \phi$

Answer

Let $y=\sin \phi$ $\Rightarrow d y=\cos \phi d \phi$
Therefore, $\int \frac{(3 \sin \phi-2) \cos \phi}{5-\cos ^{2} \phi-4 \sin \phi} d \phi$ = $\int \frac{(3 y-2) d y}{5-\left(1-y^{2}\right)-4 y}$
= $\int \frac{3 y-2}{y^{2}-4 y+4} d y$
Now, we write $\frac{3 y-2}{(y-2)^{2}}=\frac{A}{y-2}+\frac{B}{(y-2)^{2}}$
Therefore, 3y - 2 = A (y - 2) + B
Comparing the coefficients of y and constant term,
we get A = 3 and B = 4. for y = 2, y= 0
Therefore, the required integral is given by
$I=\int\left[\frac{3}{y-2}+\frac{4}{(y-2)^{2}}\right] d y$ = $3 \int \frac{d y}{y-2}+4 \int \frac{d y}{(y-2)^{2}}$
= $3 \log |y-2|+4\left(-\frac{1}{y-2}\right)+C$
= $3 \log |\sin \phi-2|+\frac{4}{2-\sin \phi}+C$
= $3 \log (2-\sin \phi)+\frac{4}{2-\sin \phi}+C$ (since, sin $\phi $ $\in$[-1,1], sin $\phi $< 2, 2 - sin $\phi $ is always positive)

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