// scilab script (matrix function)
//
// draw triangle
a1=[1.5 2 .5 1.5];
b1=[.5 2 1.5 .5];
xfpoly(a1,b1,2);
// rotation angle (radians)
theta=%pi/2;  
// rotation matrix
A=[cos(theta) -sin(theta);sin(theta) cos(theta)];
// transform
for k=1:4
  z(1)=a1(k);
  z(2)=b1(k);
  w=A*z;
  a2(k)=w(1);
  b2(k)=w(2);  
end
// draw rotated triangle
xfpoly(a2,b2,5);
square( -3,-3,3,3);
// draw a line
plot([0 1],[0 1],'b');
plot([0 -1],[0 1],'r');
//