The attachment shows my attempt at deriving the dft equation for baseband 2FSK.
Although the equation I have derived is not correct, I believe its not far away.
I have already done it for time periods Tb and 2Tb, were Tb is the bit period, and the equations seem correct.
The attached file is for 3Tb, which I am having difficulty with.
If you read the attachment it will be obvious I am not a mathematician as I have made some uniformed assumptions in an effort to get the correct answer.
By the way I have been using SIMULINK to test/prove my theory.
Many thanks