how to make the label inside this graph that arrow sin(pi/2) and how to make the grid like tht blurry and no cut line

Answer 1

[Chunru]

t = linspace(-pi, pi, 41);
x1 = sin(1*t);
x2 = sin(2*t);
plot(t, x1, 'bo-', t, x2, 'r*-');
grid on
pos = get(gca, 'Position');
xPosition = t(31);   % 31st point
yPosition = x2(31);
% Coordinates in data units
ta1 = annotation('textarrow',...
    [(xPosition +.5 + abs(min(xlim)))/diff(xlim) * pos(3) + pos(1),...
     (xPosition + abs(min(xlim)))/diff(xlim) * pos(3) + pos(1) ],... 
    [(yPosition - min(ylim))/diff(ylim) * pos(4) + pos(2),...
     (yPosition - min(ylim))/diff(ylim) * pos(4) + pos(2)]);
text(xPosition +.5 , yPosition, 'sin(\pi t/2)')
legend