在△ ABC中,角A，B，C的对边分别为a，b，c,dfrac (sin A)(sin B)=dfrac (3)(5),dfrac (sin A)(sin B)=dfrac (3)(5),c=7,则△ ABC的面积()A.dfrac (sin A)(sin B)=dfrac (3)(5) B.dfrac (sin A)(sin B)=dfrac (3)(5) C.dfrac (sin A)(sin B)=dfrac (3)(5) D.dfrac (sin A)(sin B)=dfrac (3)(5)

18.记 Delta ABC 的内角A,B,C的对边分别为a,b,c,已知-|||-dfrac (cos A)(1+sin A)=dfrac (sin 2B)(

17、单选 lim _(xarrow infty )dfrac (sin 3x+2x)(sin 2x-3x)-|||-A dfrac (1)(3)-|||-B

求lim _(xarrow infty )dfrac (sin dfrac {3)(x)}(sin dfrac {2)(x)}求

+sin dfrac (npi )(2)+... （ ）A 、是收敛的 ; B 、是收敛的，其和为sin dfrac (pi )(2)+sin dfrac (2

lim _(xarrow 0)dfrac ({x)^2sin dfrac (1)(x)}(tan x)=A.0B.1C.lim _(xarrow 0)dfrac

[题目] Delta ABC 的内角A.B.c的对边分别为ab.c,已-|||-知 sin dfrac (A+C)(2)=bsin A.-|||-(1)求B;-

设(x)=sin x, 则(dfrac (pi )(2))= __-|||-_.-|||-A cos dfrac (pi )(2)-|||-B o-|||-C-

[ dfrac (sin z)({z)^2},0] =-|||-A 1-|||-B .-1-|||-C dfrac (1)(2)

求下列函数的导数 ( 1 ) =sin dfrac (1)(x)( 2 )=sin dfrac (1)(x)( 3 )=sin dfrac (1)(x)求下列函

(3) lim _(xarrow 0)dfrac (sin 2x)(sin 5x);