令u=-t若f(x)為奇函數(shù),∫（0,x）f(t)dt記作G1(x)G1(-x) = ∫（0,-x）f(t)dt= ∫（0,x）f(-u)d(-u)= ∫（0,x）f(u)d(u)= ∫（0,x）f(t)dt=G1(x)若f(x)為偶函數(shù),∫（0,x）f(t)dt記作G2(x)G2(-x) = ∫（0,-x）f(t)dt= ...G2(-x) = ∫（0，-x）f(t)dt= ∫（0，x）f(-u)d(-u) 上面是 ∫（0，-x） 下面怎么就變成 ∫（0，x）了？ 沒看懂?? t= -u, ??t= 0???-u=0?? u=0??t = -x???-u=-x?? u=x??u??x?仯??0?? ????-u?? -x?仯??0?? ????t?? -x?仯??0????????????t????0??-x?? ?????u????0??x????????????? ??= ???0??x??f(-u)d(-u) ??= -???0??x??f(u)d(u)??????? ????? ??2??? ??????? -???0??x??f(-u)d(u) ????? -???0??x??f(u)d(u)∫（0，x）f(-u)d(-u)對(duì)d(-u)計(jì)算 d(-u) = -du= - ∫（0，x）f(-u)du偶函數(shù)f(-u) = f(u)=-∫（0，x）f(u)d(u)