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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

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) =-...

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) =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...

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° =(cot20°tan20°)·(√3cos10°) =√3cos10° =√3cos(π/18)

tan70°*cos10°*(√3 *tan20° -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°(√3tan20°-1) =sin70°cos10°(√3sin20°-cos20°)/(cos70°cos20°) =-2cos20°cos10°sin(30°-20°)/(sin20°cos20°) =-cos20°sin20°/(sin20°cos20°) = -1

tansinlim613lim31coslimsinlim222102030...10:设函数f(x)连续,且0)0(f,求极限.)()()(lim000...

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