eqn1 = gx*cos(p)*cos(y) + gy*(sin(p)*sin(r)*cos(y) - sin(y)*cos(r)) + gz*(sin(p)*cos(r)*cos(y) + sin(r)*sin(y)) - nx;
eqn2 = gx*sin(y)*cos(p) + gy*(sin(p)*sin(r)*sin(y) + cos(r)*cos(y)) + gz*(sin(p)*sin(y)*cos(r) - sin(r)*cos(y)) - nx;
eqn3 = -gx*sin(p) + gy*sin(r)*cos(p) + gz*cos(p)*cos(r) - nz;