1) F=q[vB], where q -> charge, v-> velocity, B-> magnetic field. [ , ] -> cross product.
2) f=q*v*B*sin(11°) {1}
3) 1.6f=q*v*B*sin(alpha) {2}
4) {2} / {1} -> 1.6=sin(alpha)/sin(11°) or sin(alpha)=1.6*sin(11°) --> alpha=arcsin (1.6*sin(11°))
So, alpha=17.7°=18°