3. Consider the continuous-time function $x_1(t) = 2[u(t) - u(t - 6)]$ (Note that here, $u(t)$ represents the unit step function).
a) Find the Fourier transform of $x_1(t)$ using the Fourier integral.
$X_1(\omega) = 12e^{-j3\omega}\text{sinc}(3\omega)$ (unnormalized)*
$X_1(\omega) = 12e^{-j3\omega}\text{sinc}(\frac{3\omega}{\pi})$ (normalized)*
b) Produce a MATLAB plot of the magnitude response of $X_1(\omega)$ over the linear frequency range $\omega = 0$ to 5 rad/sec.