將f(x)=cosx展開成x +π/6的幂級數,

將f(x)=cosx展開成x +π/6的幂級數,

(Cosx)2
=(1 + COS(2倍))/ 2
COS(2×)= 1 -!(2X)^ 2/2 +(2X)^ 4/4!-(2倍)^ 6/6 +…
(cosx)2 = 1 +(1/2)(-!(2×)^ 2/2 +(2×)^ 4 / 4 -(2倍)^ 6/6 + .)!