1. Let a1,a2,…,an and b1,b2,…,bm be n+m unit vectors in the r-dimensional Euclidean space Er(n,m≤r); let a1,a2,…,an as well as b1,b2,…,bm be mutually orthogonal. For any vector x∈Er, considerTx=∑i=1n∑k=1m(x,ai)(ai,bk)bk((a,b) denotes the scalar product of a and b). Show that the sequence (Tkx)k=0∞, where T0x=x and Tkx=T(Tk−1x), is convergent and give a geometrical characterization of how the limit depends on x. (S. 14)