dfrac (1)(2)pi (R)^2E-|||-D. sqrt (2)(R)^2E-|||-E. dfrac (pi {R)^2E}(sqrt {2)}

dfrac (pi {R)^2E}(2)-|||-C.2πR^2E-|||-D.0

-(pi R)^2E-|||-E-|||-R-|||-图1

sqrt (2)pi -|||-C. dfrac (sqrt {2pi )}(4)-|||-D. dfrac (sqrt {2pi )}(8)

. _(Y)(y)=dfrac (1)(2sqrt {2pi )}(e)^-dfrac (y{2)} ,gt 0-|||-bigcirc ._(Y)(y)=d

[题目]设 (x)=sqrt (1+{ln )^2x} 则 (e)=()-|||-A、 dfrac (sqrt {2)}(4)-|||-B、 dfrac (sq

[ 0,dfrac (pi )(2)] D. [ -sqrt (dfrac {pi )(2)},0]

dfrac ({mu )_(0)I}(pi R)(dfrac (1)(2)+dfrac (pi )(6))-|||-dfrac ({mu )_(0)I}(pi

设随机变量X的概率密度为(x)=dfrac (1)(2sqrt {pi )}(e)^-dfrac ({(x-3)^2)(4)}((x)=dfrac (1)(2s

(int )_(-infty )^+infty (x)^2(e)^-a(x^2)dx=dfrac (1)(2)sqrt (dfrac {pi )({a)^3}}

dfrac (2pi )(sqrt {3)} D. dfrac (pi )(6)