Proof. Introducing the substitution 8 =arccos( changes this equation Tn(0(a))=T(0)=cos(ne), where 0E[ 0, a recurrence relation is derived by noting that Tn+1(6)=c8(76)cs6)-sin(n)sin(6) ane Tm-1(0)=cos(nl)cos(0)+sin(ne)sin(A Tn+1(6)=2c0s(n6)o(6-Tn-1(6). Returning to the variable g gives Tn+(a)=2 Tn()-Tn-1(), for each n2