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(sin75+Cos75)/(Cos15%sin15)=?

cos75cos15sin75sin15分两步 cos75cos15=1/2*(cos(75+15)+cos(75-15)) sin75sin15=-1/2*(cos(75+15)-cos(75-15)) cos75cos15sin75sin15=-1/4 *( (cos90)²-(cos60)²) =-1/4*(0-0.25) =1/16

等于。

sin75°=sin(45°+30°)=sin45°cos30°+cos45°sin30°=(√6+√2)/4 cos75=cos(30+45)=cos30cos45-sin30sin45=√6/4-√2/4=(√6-√2)/4 sin75+cos75=sin75+sin15=2sin(75+15)/2cos(75-15)/2=2sin45cos30=√6/2 sin75-cos75=sin75-sin15=2cos(75+15)/2sin(75-1...

方法一:cos75°cos15°+sin75°sin15°=cos(75°-15°)=cos60°=0.5 方法二:cos75°cos15°+sin75°sin15°=sin15°cos15°+cos15°sin15°=sin15°cos15°=sin30°=0.5

cos75-cos15 =cos(45+30)-cos(45-30) =cos45cos30-sin45sin30-(cos45cos30+sin45sin30) =cos45cos30-sin45sin30-cos45cos30-sin45sin30 =-2sin45sin30 =-2*(√2)/2*1/2 =-(√2)/2

sin15°cos75° =(根号6-根号2)/4X(根号6+根号2)/4 =[(根号6-根号2)X(根号6+根号2)]/16 =(6-2)/16 =1/4

∵ . a =(cos75°,sin75°), . b =(cos15°,sin15°) ,∴ a - b =(cos75°-cos15°,sin75°-sin15°)∴| a - b |= (cos75°-cos15°) 2 +(sin75°-sin15°) 2 = 2-2(cos75°cos15°+sin75°sin15°) = 2-2cos60° =1故答案为:1

sin75°cos75° =0.5xsin150° =0.5x0.5 =0.25 由倍角公式 sin2a=2sinacosa 令a=75度 则sin(2*75)=2sin75cos75 sin150=2sin75cos75 所以1/2=2sin75cos75 所以sin75cos75=1/4 朋友,请【采纳答案】,您的采纳是我答题的动力,谢谢。

cos75°cos15°-sin255°sin15° =cos75°cos15°-sin(180°+75°)sin15° =cos75°cos15°-(-sin75°)sin15° =cos75°cos15°+sin75°sin15° =cos(75°-15°) =cos60° =1/2

显然sin105°=sin(180°-105°)=sin75° 而cos105°= -cos(180°-105°)= -cos75° 所以 sin105°cos105°+cos75°sin75° = -sin75°cos75°+cos75°sin75° =0

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