1-sin+3

於赖趴1322已知a为第二象限角,化简根号下1+2sin(5π - α)*cos(α - π)/sin(α - (2/3) *π) - 根号下1 - sin ( (3/2) *π+α )^2 -
阮士径19286572420 ______[答案] 解析:已知α为第二象限角,则有:sinα>0,cosα0原式=根号下[ 1+2sinα*(-cosα)]/{ sin(α+ 2分之π)-根号下[1-(cosα )^2 ] }=根号下( 1-2sinα*cosα)/[ cosα - 根号下(sinα )^2 ]=[根号下(sina-cosa)^2] /(co...

於赖趴1322令 An= sin1 + sin2 + ... + sin(n),证明 |An|<3 -
阮士径19286572420 ______ 2Ancos1=2sin1cos1+2sin2cos1+...+2sin(n)cos1 =sin2+sin3-sin1+sin4-sin2+sin5-sin3+sin6-sin4+...+sinn-sin(n-2)+sin(n+1)-sin(n-1) =sinn+sin(n+1)-sin1 An=[sinn+sin(n+1)-sin1]/2cos1 因为1所以cos1>1/2 即|An|=|[sinn+sin(n+1)-sin1]/2cos1|

於赖趴1322求cosθ(1 - sinθ)的最值. -
阮士径19286572420 ______[答案] [cosθ(1-sinθ)]2=(cosθ)2(1-sinθ)2=[1-(sinθ)2](1-sinθ)2=(1+sinθ)(1-sinθ)3=(3+3sinθ)3•(1-sinθ)3≤13[(3+3sinθ+1-sinθ+1-sinθ+1-sinθ]4=2716当且仅当3+3sinθ=1-sinθ即sinθ=-12...

於赖趴1322(1 - (sin^4x - sin^2xcos^2x+cos^4x)/sin^2x +3sin^2x -
阮士径19286572420 ______[答案] sin^4x-sin^2xcos^2x+cos^4x =sin^4x+2sin^2xcos^2x+cos^4x-3sin^2xcos^2x =(sin^2x+cos^2x)^2-3sin^2xcos^2x =1-3sin^2xcos^2x 所以分子=3sin^2xcos^2x 所以原式=3sin^2xcos^2x/sin^2x+3sin^2x =3cos^2x+3sin^2x =3(sin^2x+cos^2x) =3

於赖趴1322y=cos方x - sin方x+3sinx求最大值 最小值 -
阮士径19286572420 ______[答案] ∵cos²x=1-sin²x ∴y=1-2sin²x+3sinx 设sinx=x, y=-2x²+3x+1=-2(x-3/4)²+9/8 ∵-1∴最大值为9/8,最小值为x=-1时即y=5

於赖趴1322√(2+cos2 - sin²1)
阮士径19286572420 ______ 你忘了一个倍角公式:cos2a=1-2sin²a √(2+cos2-sin²1) =√[2+(1-2sin²1)-sin²1] =√[3(1-sin²1)] =√(3cos²1) =(√3)cos1 懂了吗? 希望能帮到你 O(∩_∩)O~

於赖趴1322y=1/1 - sin(x+派/3)的定义域 -
阮士径19286572420 ______ y=1/1-sin(x+π/3) 1-sin(x+π/3)≠0 sin(x+π/3)≠1 x+π/3≠π/2+2kπ(k∈z) x≠π/6+2kπ(k∈z)所以定义域为 x∈{x|x≠π/6+2kπ(k

於赖趴1322已知tanα等于三,则 1+sinα分之一加1 - sinα分之一等于多少 -
阮士径19286572420 ______[答案] 左边通分1-sin(a) 右边通分1+sin(a) 结果就是 2/(1-sin2(a)) 有tan a=3 可以推出 sin a = 3/根号10 所以sin 2(a) = 9/10 代入 得20

於赖趴1322已知sin(a+π)=1/3,π扫码下载搜索答疑一搜即得 -
阮士径19286572420 ______[答案] 已知sin(a+π)=1/3 则-sina=1/3 即sina=-1/3 因π则cosa=-√(1-sin²a)=-2√2/3 cos(-a-2π)=cos(2π+a) =cosa =-2√2/3

於赖趴1322(1)1 - 2sin30°cos30°(2)cos60°/1+sin60°+ 1/tan30°1)1 - 2sin30°cos30°(2)cos60°/1+sin60°+ 1/tan30° (1)1 - 2*1/2*√3/2 =1 - √3/2 =(2 - √3)/2 对吗? 我不知... -
阮士径19286572420 ______[答案] 1-2sin30°cos30° =1-sin60° =1-√3/2 cos60°/(1+sin60°)+ 1/tan30° =1/2/(1+√3/2 )+1/√3/3 =1/( 2+√3)+√3 =(4+2√3)/(2+√3) =(4+2√3)(2-√3)/(2+√3)(2-√3) =8-6 =2