% We define the variables that we might use using the command syms
syms t w x y X Y u_t f H;

% we assign the step function ( Heaviside(t)) as symbolic and use it   
 sym('Heaviside(t)');

% we define the function x(t)=exp(-3t)u(t)
x=exp(-3*t)*Heaviside(t)
ezplot(x);

% finding the Fourier Transform  X(w)
X=fourier(x)

% to open a new figure window use the figure command
figure
ezplot(abs(X))
X_inv=ifourier(X)
 
% to view the result more clearly
pretty(X_inv)