)-|||-则 cot (XY)=() 。-|||-A .-dfrac (1)(18) .-|||-B .dfrac (1)(18)-|||-C .dfrac (1)(6)-|||-D -dfrac (1)(6)

dfrac (1)(12)-|||-(B) dfrac (1)(2) .-|||-C dfrac (1)(8)-|||-) dfrac (1)(6)

dfrac (1)(2)-|||-C dfrac (1)(6)-|||-D . dfrac (1)(36)

dfrac (1)(6)-|||-C. dfrac (1)(2) D. dfrac (1)(3)

dfrac (1)(6)-|||-C. dfrac (1)(2) D. dfrac (1)(3)

8.已知 (A)=dfrac (1)(4) ,(B|A)=dfrac (1)(3) ,(B)=dfrac (1)(6) ,则-|||-P(A|B)=-|||-A

10、单选-|||-极限 lim _-|||-A-|||-dfrac (1)(6)-|||-B dfrac (1)(2)-|||-C -dfrac (1)(3)

0 .dfrac (1)(2) .-|||--dfrac (1)(2) . .dfrac (1)(8) .dfrac (1)(6) .dfrac (1)(24)

(B) =2, =dfrac (1)(3).-|||-(C) =1, =dfrac (1)(2). (D) =1, =-dfrac (1)(3),求指导本题解题

若a,b,c均为正数,且a+b+c=10, 则dfrac (1)(a)+dfrac (1)(b)+dfrac (1)(c)的最小值为( )A 1 B dfrac

3、设 (x,y)=arctan dfrac (x)(y), 则 (1,1)=-|||-(A)1; (B)0; (C) dfrac {1)(2),dfrac