14.设随机变量(X,Y)的概率密度为-|||-,-|||-f(x,y)= ) 1, |y|lt x, 0lt xlt 1 0,(y|x) ,fx|y(x|y).

3.求下列函数的微分:-|||-(1) =dfrac (1)(x)+2sqrt (x) =-|||-(2) =xsin 2x ;-|||-(3) =dfrac (x)(sqrt {{x)^2+1}} =-|||-(4) =(ln )^2(1-x) ;-|||-(5) =(x)^2(e)^2x ;-|||-(6) =(e)^-xcos (3-x) ;-|||-(7) =arcsin sqrt (1-{x)^2} :-|||-(8) =(tan )^2(1+2(x)^2) ;-|||-(9) =arctan dfrac (1-{x)^2}(1+{x)^2} =-|||-(10) =Asin (omega t+varphi )(A,omega ,varphi 是常数).

已知向量组0 underline (1) -1 1 3-|||-A:a1= 1 a2= 1 :B:(b)_(1)= 0 b2= 2 ,b3= 2-|||-1 0 underline (1) 1 -1证明向量组0 underline (1) -1 1 3-|||-A:a1= 1 a2= 1 :B:(b)_(1)= 0 b2= 2 ,b3= 2-|||-1 0 underline (1) 1 -1与向量组0 underline (1) -1 1 3-|||-A:a1= 1 a2= 1 :B:(b)_(1)= 0 b2= 2 ,b3= 2-|||-1 0 underline (1) 1 -1等价.

根据图形规律，最适合填入问号处的图形是：?-|||-A B C DA、AB、BC、CD、D

例6.18 计算下列极限:-|||-(3)limx-sinx

12.证明lim_(ntoinfty)((1)/(sqrt(n^2)+1)+(1)/(sqrt(n^2)+2)+...+(1)/(sqrt(n^2)+n))=1.

解方程组： ) (x)_(1)-(x)_(2)-(x)_(3)=2 2(x)_(1)-(x)_(2)-3(x)_(3)=1 3(x)_(1)+2(x)_(2)-5(x)_(3)=0 .

A 可逆，则 ^-1|=dfrac (1)(|A|)-|||-__（）A 对B 错

一个数乘以行列式,等于用这个数乘以行列式的每一个元素。A. 对B. 错

9.设二维随机变量(X,Y)的概率密度为-|||-f(x,y)= ) Axy,0lt xlt 1,0lt ylt 1 0, .-|||-则常数 A= ()-|||-A 1-|||-B 2-|||-C 3-|||-D 4

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