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★高一年级北京市东城区教研科研中心(10001) 雷晓莉一、选择题1.已知sin(α-β)cosα-cos(α-β)sinα=4/5,则β所 在的象限是( ). (A)第一象限或第二象限 (B)第二象限 (C)第三象限或第四象限 (D)第二象限或第四象限2.设sinθ为有理数,下列各函数中,一定是有理数的 是( ). (A)cosθ (B)tanθ (C)sin2θ (D)cos2θ3.若等腰三角形顶角的正弦值为24/25,则底角的余弦值 为( ).(A)4/5 (B)3/5 (C)3/5或4/5 (D)3/4
★ Grade one of Beijing Dongcheng District Education Research Center (10001) Lei Xiaoli 1. Multiple choice questions 1. Known sin(α-β)cosα-cos(α-β)sinα=4/5, the quadrant in which β lies Yes (). (A) The first quadrant or the second quadrant (B) The second quadrant (C) The third quadrant or the fourth quadrant (D) The second quadrant or the fourth quadrant 2. Set sin θ as a rational number, the following functions In the middle, the rational number must be (). (A) cosθ (B) tanθ (C) sin2θ (D) cos2θ3. If the sine of the isosceles triangle vertex angle is 24/25, the cosine of the base angle is () .(A)4/5 (B)3/5 (C)3/5 or 4/5 (D)3/4