@ankitgupta.1729
@Satbir
Say, for an equation $a_{n}$, if the equation converges, then $\lim_{n\rightarrow \infty}a_{n}=0.$ But here it comes $3,$ which means here function diverges. So, to make it convergent, we inverses it.
right??
Please check some questions of 1993 below, It involved Fourier series, double integral etc.
limit, convergence-divergence, double integral is in syllabus. These thing are not out of syllabus. But fourier series not in syllabus now.