So, ∫ − T 2 T 2 e j 2 π ( n − m ) t / T d t = { T , for n = m 0 , for n ≠ m {\displaystyle \int _{-{\frac {T}{2}}}^{\frac {T}{2}}e^{j2\pi (n-m)t/T}dt={\begin{cases}T,&{\mbox{for }}n=m\\0,&{\mbox{for }}n\neq m\end{cases}}\!}
