[" 4.Show that the vectors "vec a,b" and "vec c" are coplanar if "vec a+vec b,vec b+vec c" and "vec c+vec a" are cop "],[2.36" 1.For any three vectors "vec a,vec b" and "vec c" are prove that "vec a-vec b,vec b-vec b" and "vec c-vec a" and "vec c-vec a" and "vec c+vec a" are coplan "]