MATLAB example
To plot the function e^-t/2 cos(2 pi t/1.5 + 45^o):

TC = 2;
tmax = 5*TC;
t = 0:tmax/1000:tmax;
v = exp(-t/2).*cos(2*pi*t/1.5 + 45*pi/180);
plot(t,v);
grid
xlabel('t (seconds)');
ylabel('v (volts)');
title('Plot of e^{-t/2} cos(2 \pi t/1.5 + 45^o)');