一、选择题-|||-1. sin (20)^circ cos (10)^circ -cos (160)^circ sin (10)^circ =-|||-()-|||-A. -dfrac (sqrt {3)}(2) B. dfrac (sqrt {3)}(2) C. -dfrac (1)(2) D. dfrac (1)(2)-|||-2. (sin )^4(15)^circ -(cos )^4(15)^circ = ()-|||-A. dfrac (1)(2) B. -dfrac (1)(2) C. dfrac (sqrt {3)}(2) D. -dfrac (sqrt {3)}(2)-|||-3. 已知点A在圆 ^2+(y)^2=4 上,-|||-且 angle xOA=dfrac (7)(12)pi , 则点A的横坐标为 ()-|||-A. dfrac (sqrt {2)-sqrt (6)}(2) B. dfrac (sqrt {2)-sqrt (6)}(4) C. dfrac (1-sqrt {3)}(4) D. dfrac (1-sqrt {3)}(2)-|||-4.在 Delta ABC 中, tan A+tan B+sqrt (3)=sqrt (3)tan Atan B, 则C等于-|||-()-|||-A. dfrac (pi )(3) B. dfrac (2pi )(3) C. dfrac (pi )(6) D. dfrac (pi )(4)-|||-.5. 已知 sin (alpha +dfrac (pi )(3))+cos (alpha -dfrac (pi )(2))-|||-=-dfrac (4sqrt {3)}(5), 则 cos (alpha +dfrac (2pi )(3))= ()-|||-A. dfrac (sqrt {5)}(2) B. -dfrac (3)(5) C. dfrac (4)(5) D. dfrac (3)(5)-|||-6.公元前6世纪,古希腊的毕达哥拉斯学派研究过正五边形-|||-和正十边形的作图方法,发现了黄金分割,其比值约为-|||-0.618,这一数值也可以表示为 =2sin (18)^circ , 若 ^2+n=4,-|||-则dfrac (msqrt {n)}(2{cos )^2(27)^circ -1}= (C-|||-A.8 B.4 C.2 D.1-|||-7.设 =cos (50)^circ cos (127)^circ +cos (40)^circ sin (127)^circ , =dfrac (sqrt {2)}(2)(sin (56)^circ --|||-cos56°), =dfrac (1-{tan )^2(39)^circ }(1+{tan )^2(39)^circ } 则a,b,c的大小关系是 ()-|||-A. gt bgt c B. gt agt c C. gt agt b D. gt cgt b-|||-8. 若 sin 2alpha =dfrac (sqrt {5)}(5) sin (beta -alpha )=dfrac (sqrt {10)}(10).-|||-且 alpha in [ dfrac (pi )(4),pi ] beta in [ pi ,dfrac (3pi )(2)] , 则 alpha +beta 的值是(B-|||-A. dfrac (9pi )(4) B. dfrac (7pi )(4) C. dfrac (5pi )(4) 或 dfrac (7pi )(4) D. dfrac (5pi )(4) 或dfrac (9pi )(4)