sine wave

Vm = 7;
f = 50;
phi = -45*pi/180;
t = linspace(0,0.05,101);
v = Vm*cos(2*pi*f*t+phi);
plot(t,v,'k','LineWidth',2);
grid
set(gca,'FontSize',14);
xlabel('time (sec)','FontSize',18);
ylabel('voltage (volts)','FontSize',18);