Let f (x) = K / (1 + x ^ 2), - 1 be the probability density function of random variables

Let f (x) = K / (1 + x ^ 2), - 1 be the probability density function of random variables

1.∫k/(1+x^2)dx=1-->k=2/π
2.E(x)=(2/π).∫x/(1+x^2)dx=0
3.D(x)=)=(2/π).∫x^2/(1+x^2)dx=4/π-1