[nooonuii]

ข้อความเดิมเขียนโดยคุณ CHP Stannis

$$\int [Re(e^{ix})]^2dx = Re(\int e^{i2x})dx $$

$\displaystyle\int [Re(e^{ix})]^2dx=\int \cos^2 x \,dx$

แต่

$\displaystyle Re(\int e^{i2x}dx)=\int \cos 2x \, dx$