For comparison with other CAS choose from: Axiom Derive Maple Mathematica Reduce
plot3d(sin(%pi*sin(x+y)), x, -3, 3, y, -3, 3);
plot3d(tan(x*y), x, -2/3*%pi, 2/3*%pi, y, -2/3*%pi, 2/3*%pi);