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tAn70Cos10

原式 =cos10(tan60-tan70) =cos10(sin60/cos60-sin70/cos70) =cos10(sin60cos70-sin70cos60)/cos60cos70 =cos10sin(60-70)/(1/2)cos70 =2cos10sin(-10)/sin20 =-2cos10sin10/sin20 =-sin20/sin20 =-1 满意请采纳

将tan化成sin/cos的形式 利用倍角公式和和角公式化简 代数式的值=-1 过程如下图:

tan70cos10*(√3tan20-1) =sin70/cos70*cos10*(√3sin20/cos20-1) =cos20/sin20*cos10*(√3sin20-cos20)/cos20 =cos10*(√3sin20-cos20)/sin20 =(√3sin20-cos20)/(2sin10) =(1/sin10)*(sin20cos30-cos20sin30) =1/sin10*sin(20-30) =-1

√3*tan20º -1=√3sin20º/cos20º-1=(√3sin20º-cos20º)/cos20º=2*(√3/2sin20º-1/2cos20º)/cos20º =2*sin(20º-30º)/cos20º=2sin(-10º)= - 2sin10º/cos20º 所以原式= - ...

cos10/tan20+√3sin10tan70-2cos40 =cos10/cot70+√3sin10tan70-2cos40 =cos10tan70+√3sin10tan70-2cos40 =tan70(cos10+√3sin10)-2cos40 =tan70*2sin(10+30)-2cos40 =2(tan70sin40-cos40) =2(cot20sin40-cos40) =2[(cos20sin40)/sin20-cos40] =2[(...

tan70×cos10×(√3tan20-1) =tan70×cos10×(tan60×tan20-1) =tan70×cos10×[(sin60×sin20/cos60×cos20)-1] =tan70×cos10×(sin60×sin20-cos60×cos20)/(cos60×cos20) =tan70×cos10×[-cos(60+20)]/(cos60 ×cos20) =-tan70×cos10×cos80/(cos60×cos20) =-...

tan70°cos10°+(√3)sin10°tan70°-2cos40° =tan70﹙cos10+√3sin10﹚-2cos40 =2tan70﹙1/2cos10+√3/2sin10﹚-2cos40 =2tan70sin﹙10+30﹚-2cos40 =2cos20/sin20×﹙2sin20cos20﹚-2cos40 =4cos20-2﹙2cos20-1﹚ =2 满意请采纳

你好 cos10°/tan20°+√3sin10°tan70°-2cos40° =cos10°cos20°/sin20°+√3sin10°sin70°/cos70°-2cos40° =cos10°cos20°/sin20°+√3sin10°cos20°/sin20°-2cos40° =2cos20°/sin20°(1/2cos10°+√3/2sin10°)-2cos40° =2cos20°/sin20°*sin(30°+10°)-2cos...

tan70°cos10°(√3tan20°-1) =sin70°/cos70°×cos10°(√3sin20°/cos20°-1) =sin70°×cos10°(√3sin20°-cos20°)/cos70°cos20° =2cos20°×cos10°(√3/2sin20°-1/2cos20°)/cos70°cos20° =2×cos10°(sin60sin20°-cos20°cos20°)/cos70° =-2×cos10°×cos80°/co...

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