sin wdo 则 O π2 π <0 2 +0 sin at dw 二 0, =0 0 π-2 >0 t 1 0, t<0 2   > < = + =          > = − < = = ∫ ∫ ∫ +∞ +∞ +∞ 1, 0 0, 0 d 1 sin 2 1 ( ) , 0 2 0, 0 , 0 2 d sin , 2 d sin 0 0 0 t t t f t t t t t ω ω ω π π π ω ω ω π ω ω ω 因为 则