因为f（x）是
随机变量x的
概率密度函数所以
∫f(x)d(x)│(x=-
∞
to
+∞)=1
又因为
f（x）=f（-x）
所以
∫f(x)d(x)│(x=-
a
to
0)=∫f(x)d(x)│(x=0
to
a
)
F(0)=∫f(x)d(x)│镇悔(x=-
∞
to
0)=∫f(x)d(x)│(x=0
to
+∞
)=(1/御昌正2)*∫迅姿f(x)d(x)│(x=-
∞
to
+∞)=1/2
F(-a)=∫f(x)d(x)│(x=-
∞
to
-a)=∫f(x)d(x)│(x=-
∞
to
0)-∫f(x)d(x)│(x=-
a
to
0)=1/2-∫f(x)d(x)│(x=0
to
a
)
