Step 1: Recall trigonometric values at standard angles
From trigonometry,
\[
\cos 0^\circ = 1, \cos 90^\circ = 0, \cos 180^\circ = -1.
\]
Step 2: Apply for $0^\circ$
Thus, directly,
\[
\cos 0^\circ = 1.
\]
Step 3: Conclusion
Therefore, the value of $\cos 0^\circ$ is $1$.
The correct answer is option (A).
The value of $\dfrac{1+\cot^2 \theta}{1+\tan^2 \theta}$ will be: