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Refine mathematical expressions in markdown file by improving clarity and coherence. Replace redundant phrases and enhance the structure of integral inequalities for better readability.
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‎content/数学分析/复值可测函数的L积分.md‎

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@@ -110,7 +110,7 @@ $$\int \overline{\mathbf{f}} d\mu = \int u d\mu - i \int v d\mu = \overline{\int
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$$\text{Re}\,\mathbf{f} = \text{Re}\,\mathbf{g} \quad \text{a.e.} \quad \text{且} \quad \text{Im}\,\mathbf{f} = \text{Im}\,\mathbf{g} \quad \text{a.e.}$$
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根据您给出的性质 4(实值 a.e. 相等函数积分相等):
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因此
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$$\int \text{Re}\,\mathbf{f} d\mu = \int \text{Re}\,\mathbf{g} d\mu \quad \text{且} \quad \int \text{Im}\,\mathbf{f} d\mu = \int \text{Im}\,\mathbf{g} d\mu$$
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@@ -123,8 +123,6 @@ $$\int \text{Re}\,\mathbf{f} d\mu = \int \text{Re}\,\mathbf{g} d\mu \quad \text{
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**欲证**:$\left| \int \mathbf{f} d\mu \right| \le \int |\mathbf{f}| d\mu$
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> **证明思想**:由于左边是一个**复数**的模长,直接复展开极为繁琐。我们采用分析学中经典的“复旋转法”(利用极坐标思想将复数旋转至实轴)进行极优雅的严格证明。
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**证明**:
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设复数积分值 $z = \int \mathbf{f} d\mu \in \mathbb{C}$。
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@@ -151,7 +149,7 @@ $$|z| = \int \text{Re} \left( e^{-i\theta} \mathbf{f} \right) d\mu$$
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$$\text{Re} \left( e^{-i\theta} \mathbf{f} \right) \le \left| e^{-i\theta} \mathbf{f} \right| = \left|e^{-i\theta}\right| \cdot |\mathbf{f}| = 1 \cdot |\mathbf{f}| = |\mathbf{f}|$$
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由于上述不等式处处成立,利用实值 $L$ 积分的单调性(性质 11 中的单调性):
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由于上述不等式处处成立,利用实值 $L$ 积分的单调性:
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$$|z| = \int \text{Re} \left( e^{-i\theta} \mathbf{f} \right) d\mu \le \int |\mathbf{f}| d\mu$$
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