fourier transform

[skan]

hi ,

the question is to find the fourier transform of the following eqn without using integration

d(t)= [c(-1.5t)]exp(jwat)

where
c(t)= Ao + E(Sumation)An*cos(nwot) + Bn sin(nwot) [fourier series formula]

I knwo to find the FT of the above fourier series. But why is exp(jwat)
the frequency shift and why shud we shift by wa.

Thanks,
skan