function[m1]=i1sin(a,b,x0,v)
if a<=x0-v
a1=-1;
else
a1=(a-x0)/v;
end
if b>=x0+v
b1=1;
else
b1=(b-x0)/v;
end

m1=(x0/pi)*(asin(b1)-asin(a1))+(v/pi)*(sqrt(1-a1^2)-sqrt(1-b1^2));