mona+cosplay
@沈马4272：化简:cos²1°+cos²2°+...+cos²89° - 作业帮
谢亮15313538804…… [答案] 原式=cos²(90°-89°)+cos²(90°-88°)+……+cos²88°+cos²89° =sin²89°+sin²88°+……+cos²45°+……cos²88°+cos²89° =(sin²89°+cos²89°)+(sin²88°+cos²88°)+……(sin²46²+cos²46°)+cos²45° =1+1+……+1+(√2/2)² 有44个1...
@沈马4272：化简 cos(a - 15°)+cos(a+45°) - 根号3*cos(a+15°)来人啊还有一个f(x)=sinx+cosx 若π/4
谢亮15313538804…… [答案] 【 cos(a-15°)+cos(a+45°)】 - 根号3*cos(a+15°) =2*cos{[(a-15°)+(a+45°)]/2} *cos{[(a-15°)-(a+45°)]/2} - 根号3*cos(a+15°) =2*cos(a+15°)cos(-30°) - 根号3*cos(a+15°) =2*cos(a+15°)cos3...
@沈马4272：cos²1°+cos²2°+cos²3°+cos²4°……………cos²89° - 作业帮
谢亮15313538804…… [答案] cos²1°+cos²2°+cos²3°+cos²4°……………cos²89°=cos^2(1°)+cos^2(89°)+cos^2 (2°)+cos^2 (88°)+.+cos^2(45°)=sin^2(1°)+cos^2(1°)+sin^2 (2°)+cos^2 (2°)+sin^2(90°)+....
@沈马4272：化简(cos^2 a/sina+sina)*tana -
谢亮15313538804…… (cos^2 a/sina+sina)*tana=(1-2sin^2 a)/sina+sina)*tana=((1/sina-2sina)+sina)*tana=(1/sina(1-sin^2 a))*sina/cosa=cos^2a/cosa=1/cosa
@沈马4272：cos( - 派/6)+cos(派 - 派/6)cos(2派 - 派/6)+cos(3派 - 派/6)+……+cos(2010派 - 派/6),化...cos( - 派/6)+cos(派 - 派/6)cos(2派 - 派/6)+cos(3派 - 派/6)+…... - 作业帮
谢亮15313538804…… [答案] =cos(-30)+cos150+cos(330)+cos510.+cos(2010π-30) =cos30-cos(30)+cos30-cos30.+cos30 =cos30+0+0+0...+0 =cos30 =√3/2
@沈马4272：求cos1+cos2+cos3+…+cos178+cos179的值 - 作业帮
谢亮15313538804…… [答案] COSx+COS(180-x)=COSx-COSx=0 cos1+cos179=0 cos2+cos178 =0 ………… cos1+cos2+cos3+…+cos178+cos179 =(cos1+cos179)+(cos2+cos178)+(cos3+cos177)…… =0
@沈马4272：cos²α+cos²(120° - α)+cosαcos(120° - α)化简cos²α+cos²(120° - α)+cosαcos(120° - α) - 作业帮
谢亮15313538804…… [答案] x=60°-α 则,通过积化和差与和差化积 原式化为 cos(x-60)^2+cos(x+60)^2+cos(x-60)cos(x+60) =(cos(x-60)+cos(x+60))^2-cos(x-60)cos(x+60) =cosx^2-cosx^2*(1/4)+sinx^2*(3/4) =3/4
@沈马4272：已知i1=10sin (1000t+30º) A,i2=10cos (1000t - 10º) A,则i1相位比...
谢亮15313538804…… 三内角A,B,C的大小为等差数列 A+B+C=π,A+C=2B,可得3B=π,即B=π/3 A+C=2π/3
@沈马4272：cos²79°+cos²41° - 2cos79°*cos41°*cos120°的值为 - 作业帮
谢亮15313538804…… [答案] (1+cos158)/2 +(1+cos82)/2 +cos79cos41 =1-cos22 /2 +cos82/2 +cos79cos41 =1+1/2(cos82-cos22)+cos79cos41 =-sin52sin30+cos79cos41+1 =-sin52 /2 +1/2(cos120+cos38) +1 =-sin52 /2+cos38/2 +3/4 =3/4
谢亮15313538804…… [答案] 原式=cos²(90°-89°)+cos²(90°-88°)+……+cos²88°+cos²89° =sin²89°+sin²88°+……+cos²45°+……cos²88°+cos²89° =(sin²89°+cos²89°)+(sin²88°+cos²88°)+……(sin²46²+cos²46°)+cos²45° =1+1+……+1+(√2/2)² 有44个1...
@沈马4272：化简 cos(a - 15°)+cos(a+45°) - 根号3*cos(a+15°)来人啊还有一个f(x)=sinx+cosx 若π/4
@沈马4272：cos²1°+cos²2°+cos²3°+cos²4°……………cos²89° - 作业帮
谢亮15313538804…… [答案] cos²1°+cos²2°+cos²3°+cos²4°……………cos²89°=cos^2(1°)+cos^2(89°)+cos^2 (2°)+cos^2 (88°)+.+cos^2(45°)=sin^2(1°)+cos^2(1°)+sin^2 (2°)+cos^2 (2°)+sin^2(90°)+....
@沈马4272：化简(cos^2 a/sina+sina)*tana -
谢亮15313538804…… (cos^2 a/sina+sina)*tana=(1-2sin^2 a)/sina+sina)*tana=((1/sina-2sina)+sina)*tana=(1/sina(1-sin^2 a))*sina/cosa=cos^2a/cosa=1/cosa
@沈马4272：cos( - 派/6)+cos(派 - 派/6)cos(2派 - 派/6)+cos(3派 - 派/6)+……+cos(2010派 - 派/6),化...cos( - 派/6)+cos(派 - 派/6)cos(2派 - 派/6)+cos(3派 - 派/6)+…... - 作业帮
谢亮15313538804…… [答案] =cos(-30)+cos150+cos(330)+cos510.+cos(2010π-30) =cos30-cos(30)+cos30-cos30.+cos30 =cos30+0+0+0...+0 =cos30 =√3/2
@沈马4272：求cos1+cos2+cos3+…+cos178+cos179的值 - 作业帮
谢亮15313538804…… [答案] COSx+COS(180-x)=COSx-COSx=0 cos1+cos179=0 cos2+cos178 =0 ………… cos1+cos2+cos3+…+cos178+cos179 =(cos1+cos179)+(cos2+cos178)+(cos3+cos177)…… =0
@沈马4272：cos²α+cos²(120° - α)+cosαcos(120° - α)化简cos²α+cos²(120° - α)+cosαcos(120° - α) - 作业帮
谢亮15313538804…… [答案] x=60°-α 则,通过积化和差与和差化积 原式化为 cos(x-60)^2+cos(x+60)^2+cos(x-60)cos(x+60) =(cos(x-60)+cos(x+60))^2-cos(x-60)cos(x+60) =cosx^2-cosx^2*(1/4)+sinx^2*(3/4) =3/4
@沈马4272：已知i1=10sin (1000t+30º) A,i2=10cos (1000t - 10º) A,则i1相位比...
谢亮15313538804…… 三内角A,B,C的大小为等差数列 A+B+C=π,A+C=2B,可得3B=π,即B=π/3 A+C=2π/3
@沈马4272：cos²79°+cos²41° - 2cos79°*cos41°*cos120°的值为 - 作业帮
谢亮15313538804…… [答案] (1+cos158)/2 +(1+cos82)/2 +cos79cos41 =1-cos22 /2 +cos82/2 +cos79cos41 =1+1/2(cos82-cos22)+cos79cos41 =-sin52sin30+cos79cos41+1 =-sin52 /2 +1/2(cos120+cos38) +1 =-sin52 /2+cos38/2 +3/4 =3/4
