已知为锐角,cos( 15度)=3 5
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因为sinα=3cosα两边平方(sinα)^2=9(cosα)^2得(cosα)^2=1/10sinαcosα=3((cosα)^2)=3/10
∵α为锐角∴cosα>0∵tanα=√2-1==>sinα/cosα=√2-1==>sinα=(√2-1)cosα==>((√2-1)cosα)^2+(cosα)^2=1(∵(sinα)^2+(cos
设在直角三角形ABC中,∠A=α,∠C=90°,故sinα=ac,cosα=bc;则m=sinα+cosα=a+bc>1.故选A.
a=45°
α为锐角,tanα=根号3,a=60度cosa=cos60度=1/2
1、cos(π/4-α)2、543、0.5
sinacosa=1/8(sina+cosa)²=sin²a+2sinacosa+cos²a=1+1/4=5/4a为锐角,于是sina+cosa>0所以sina+cosa
展开后有cosacosβ-sinasinβ=sinacosβ-cosasinβ移项后cosa(sinβ+cosβ)=sina(sinβ+cosβ)a、β是锐角,(sinβ+cosβ)≠0,约掉cosa
1、tana=1/2=sina/cosa2sina=cosa4sin^2a=cos^2a4(1-cos^2a)=cos^2acosa=2倍根5/5(因为a为锐角)2、Sin2aCosa-Sina/Si
因为a为锐角,且cos(a+pi/4)=3/5所以0〈a+pi/4
令cosθ=ty^2=(1-t^2)*t^2*t^2=(1-t^2)*(t^2/2)*(t^2/2)*4≤((1-t^2+t^2)/3)^3*4=4/27所以y≤2√3/9当cosθ=√3/3取等号
角A为锐角,sin(A+15°)=4/5,∴cosA=cos[(A+15°)-15°]=cos(A+15°)cos15°+sin(A+15°)sin15°>0,∴cos(A+15°)=3/5,∴sin
(sina+cosa)^2+(sina-cosa)^2=(sina)^2+2sinacosa+(cosa)^2+(sina)^2-2sinacosa+(cosa)^2=2*((sina)^2+(cos
∵α为锐角,且cos(α+π6)=45,∴sin(α+π6)=35,∴cosα=cos[(α+π6)-π6]=cos(α+π6)cosπ6+sin(α+π6)sinπ6=45•32+35•12=43+
m=sinα+cosα=√2*(√2/2*sinα+√2/2*cosα)=√2*(sinαcosπ/4+cosαsinαπ/4)=√2*sin(α+π/4)α为锐角0
再问:你能写清楚点么再答:那个不清楚?
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