weiyuntian
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共回答了14个问题采纳率:85.7% 举报
令u=-t
若f(x)为奇函数,∫(0,x)f(t)dt记作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)为偶函数,∫(0,x)f(t)dt记作G2(x)
G2(-x) = ∫(0,-x)f(t)dt
= ∫(0,x)f(-u)d(-u)
= -∫(0,x)f(u)d(u)
= -∫(0,x)f(t)dt
=G2(x)
1年前
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8
xllj_wang
举报
G2(-x) = ∫(0,-x)f(t)dt = ∫(0,x)f(-u)d(-u) 上面是 ∫(0,-x) 下面怎么就变成 ∫(0,x)了? 没看懂
举报
weiyuntian
t= -u, t= 0ʱ-u=0 u=0 t = -xʱ-u=-x u=x ux仯0 -u -x仯0 t -x仯0Դ֮ tġң0-x ͱɶuġң0x
xllj_wang
举报
һ = ң0xf(-u)d(-u) һʽ = -ң0xf(u)d(u) ʽ һʽ ô 䵽2ʽ Ӧ -ң0xf(-u)d(u) Ϊʲô -ң0xf(u)d(u)
举报
weiyuntian
∫(0,x)f(-u)d(-u) 对d(-u)计算 d(-u) = -du = - ∫(0,x)f(-u)du 偶函数f(-u) = f(u) =-∫(0,x)f(u)d(u)