江画工太猩院 (2)求余弦级数.对f(x)进行偶延拓, (x+1)x=+2, 优叭 a, =h(x+1)cos ndx 0当n=2,4,6, cosM兀 1) 当n=1,3,5, x+1=+1-(cosx+2C03x+2c0s5x+… 2 (0≤x≤)江西理工大学理学院 (2)求余弦级数. 对f ( x )进行偶延拓 , ∫ π + π = 0 0 ( 1 ) 2 a x dx = π + 2 , ∫ + π = π 0 ( 1 )cos 2 a x nxdx n (cos 1 ) 2 2 π − π = n n ⎪⎩ ⎪ ⎨ ⎧ = π − = = L L 1 , 3 , 5 , 4 0 2 , 4 , 6 , 2 n n n 当 当 cos 5 ] 5 1 cos 3 3 1 (cos 4 1 2 1 + 2 + 2 + L π + − π x + = x x x ( 0 ≤ x ≤ π )