function v = INV_half_sin(x)
%

%v = (sin(x*2*pi+pi/2)+1)/2;
%v = (sin(2*([pi/4:0.01:2*pi-pi/4]+3*pi/2))+1)/2);

t = x*3*pi/2;
v = (sin(2*t+3*pi/2)+1)/2;
