题目内容

求三角函数式的值:

(1)sin495°·cos(-675°);

(2)sin(-1200°)·tan(-)-cos585°·tan().

答案:
解析:

  解析:(1)sin495°·cos(-675°)

  =sin(135°+360°)·cos675°=sin135°·cos315°

  =sin(180°-45°)·cos(360°-45°)=sin45°·cos45°

  =×

  (2)sin(-1200°)·cot-cos585°·tan()

  =-sin1200°·-cos585°·

  =-sin(120°+3×360°)·+cos(225°+360°)·

  =-sin120°·+cos225°·

  =-sin(180°-60°)·+sin(180°+45°)

  =-sin60°·

  =cos60°-sin45°=


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