i have a short understanding question on the subject of Fourier Transformation. My task is and here I would like to quote: "A periodic signal is given, calculate the continuous time Fourier transform".

On the sketch at the task a rectangle is shown, which has its symmetry axis on the y axis. This is now repeated with a period of T. So far so good.

My question: I have a periodic signal and to my knowledge the Fourier series is used for periodic signals. For non-periodic signals the Fourier transform is used. That is correct, isn't it? But that means that the task is wrong?!

The calculation as itself I would solve, but the question about the Fourier series or the Fourier transformation from above arises.