Sampling and aliasing with Matlab

1. Write following in Matlab and test

a) t=1.00:0.01:2.00

b) Using t =>x=cos(2*pi*t)+2*sin(4*pi*t)

c) plot x %matlab -syntax?

d) plot abs(x) %matlab -syntax?

2. Using code and function x=cos(2*pi*t)+2*sin(4*pi*t), when supposed maximum value for signal frequency is 5 make plots with dots ('*'), when

a) f_s =8

b) f_s = 10

c) f_s = 50