Step 1: Separate variables.
We are given the differential equation:
\[
\frac{dy}{dx} - \sin x \sin y = 0
\]
Rearrange the equation to separate the variables:
\[
\frac{dy}{dx} = \sin x \sin y
\]
This can be written as:
\[
\frac{dy}{\sin y} = \sin x \, dx
\]
Step 2: Integrate both sides.
Now, integrate both sides of the equation:
\[
\int \frac{dy}{\sin y} = \int \sin x \, dx
\]
Step 3: Use standard integrals.
The integral of \( \frac{1}{\sin y} \) is \( \ln | \tan \frac{y}{2} | \), and the integral of \( \sin x \) is \( -\cos x \). Thus, we have:
\[
\ln \left| \tan \frac{y}{2} \right| = -\cos x + C
\]
Step 4: Simplify the result.
Exponentiating both sides to eliminate the logarithm:
\[
\left| \tan \frac{y}{2} \right| = e^{-\cos x + C}
\]
Since \( e^C \) is just a constant, we can write:
\[
\tan \frac{y}{2} = C e^{\cos x}
\]
Step 5: Conclusion.
Thus, the solution to the differential equation is:
\[
e^{\cos x} \cdot \tan \frac{y}{2} = C
\]
corresponding to option (A).