求下列分布函数所对应的概率密度:
(1)F1(x)=1/2+(1/π)arctanx,-∞﹤x﹤+∞;
(2)F2(x)=
{1-e-(x2/2),x﹥0,
0,x≤0;
(3)F3(x)=
{0,x﹤0,
sinx,0≤x≤π/2
1,x﹥π/2.
(1)f1(x)=F'1(x)=1/π(1+x2)(-∞﹤x﹤+∞) (2)f2(x)=F'2(x)= {xe-(x2/2) x﹥0 0 x≤0 (3)f3(x)=F'3(x)= {cosx 0≤x≤π/2 0 其他
求下列分布函数所对应的概率密度:
(1)F1(x)=1/2+(1/π)arctanx,-∞﹤x﹤+∞;
(2)F2(x)=
{1-e-(x2/2),x﹥0,
0,x≤0;
(3)F3(x)=
{0,x﹤0,
sinx,0≤x≤π/2
1,x﹥π/2.
(1)f1(x)=F'1(x)=1/π(1+x2)(-∞﹤x﹤+∞) (2)f2(x)=F'2(x)= {xe-(x2/2) x﹥0 0 x≤0 (3)f3(x)=F'3(x)= {cosx 0≤x≤π/2 0 其他