%外界聲壓斜入射
%st1^2+st2^2+st3^2=1;
%st1,st2,st3入射角余弦（平面波方向余弦）
%[st1,st2,st3]與[0,-tan(st),1]不成比例
st1=1/2;
st2=1/2;
st3=-(1/2)^(1/2);
Lx=0.1;
Ly=0.2;
Lz=1;
st=0;
A1=[st1,st2,st3;0,-tan(st),1;1,0,0];
A2=[st2*Ly+st3*(Lz+Ly/2*tan(st)),Lz-Ly/2*tan(st),Lx]';
A3=A1\A2;
yy=A3(2);
B1=[st1,st2,st3;0,-tan(st),1;0,1,0];
B2=[st2*Ly+st3*(Lz+Ly/2*tan(st)),Lz-Ly/2*tan(st),0]';
B3=B1\B2;
xx=B3(1);
if (xx>=0&&xx<=Lx)||(yy>=0&&yy<=Ly)
    y=abs(st1*xi+st2*yi+st3*zi-st1*Lx-st2*Ly-st3*(Lz+Ly/2*tan(st)));
else 
    y=abs(st1*xi+st2*yi+st3*zi-st2*Ly-st3*(Lz+Ly/2*tan(st)));
end
y