MATLAB: I want to use a single sine gen and then phase shift it by 90. please help in this… Is it possible ? Please Help

Question

 i want to use a single sine gen and then phase shift it by 90.
 please help in this...

And also i wanted to know how to design all pass filter

Answer 1

t = linspace(0,2*pi) ;
x = sin(pi/4*t) ;
plot(t,x,'r')
hold on
x = sin(pi/4*t+pi/2) ;  % phase shift by pi/2, which is same as cos 
plot(t,x,'b')