to find fourier transform of e^-t u(t). How do i remove this error

syms t

>> y=ftransform(exp(-t),-20,20)

Unrecognized function or variable 'ftransform'.

>> y=fft(exp(-t),-20,20)

Error using fft

Invalid data type. First argument must be double, single, int8, uint8, int16, uint16, int32, uint32, or logical.

Answer 1

[Star Strider]

The fourier function does not allow limits, so that integration would need to be done manually:

syms t omega 
y = int(exp(-t).*exp(1j*omega*t), t, -20, 20)
y = simplify(y, 150)
y = rewrite(y, 'sincos')

producing:

y =
(2*sin(20*omega + 20i)*(omega - 1i))/(omega^2 + 1)

In LaTeX:

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