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Let the distribution function of random variable X be f (x) = a + the distribution function of known random variable X be f (x) = a + B arctanx, find the values of a and B, and find P (- 1) （1）∵F(-∞)=0，F(+∞)=1 im(x→-∞)F(x)=A-Bπ/2=0; LIM (x → + ∞) f (x) = a + B π / 2 = 1; why use a minus sign and a plus sign here? How does π / 2 come from How can A-B π / 2 = 0 be solved? Bπ/2=1/2？ Why?
lim(x→-∞)F(x)=A-Bπ/2=0;
lim(x→+∞)F(x)=A+Bπ/2=1;
This is the definition of distribution function
So a = 1 / 2; b = 1 / π;
P(-1
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