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

(sin75+cos75)/(cos15-sin15) =√2×(cos45°sin75°+sin45°cos75°)/[√2×(cos45°cos15°-sin45°sin15°)] =sin(45°+75°)/cos(45°+15°) =sin120°/cos60° =(√3/2)/(1/2) =√3

见图

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

解:原式=cos(75°-15°) (应用余弦差角公式) =cos60° =1/2。

0.5

sin75°=sin(45°+30°)=sin45°cos30°+cos45°sin30°=(√6+√2)/4 cos75=cos(30+45)=cos30cos45-sin30sin45=√6/4-√2/4=(√6-√2)/4

原式=cos(75°-15°)=cos60°=1/2 望采纳,谢谢 公式:cosAcosB+sinAsinB=cos(A-B) 望采纳,谢谢

∵ . 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

等于。

cos^2(15°)+cos^2(75°)+sin15°*sin75° =cos^2(15°)+sin^2(15°)+sin15°cos15° =1+sin30°/2 =1+1/4 =5/4 希望对你有所帮助 还望采纳~~

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