√6sin(A π 4)

sin(-6π-a)cos(4π+a)=sin(-a)cos(a)=-sinacosa=-1/(1/sinacosa)=-1/[(sin²a+cos²a)/sinacosa]=-1

(sina)^6+(cosa)^6=(sin^a+cos^a)*[(sina)^4+(cosa)^4-sin^a*cos^a]=(sina)^4+(cosa)^4-sin^a*cos^a=[(sin^

sin(a-B)cosa-1/2[sin(2a+B)-sinB]=[sin(a-B+a)+sin(a-B-a)]/2-sin(2a+B)/2+sinB/2=sin(2a-B)/2+sin(-B)/2-

/>a是锐角π/2

最后结果是1.5吧?1=(sin^2a+cos^2a)^2=sin^4+2sin^2a×cos^2a+cos^4a可以明白?1-sin^6a-cos^6asin^4a+2sin^2a×cos^2a+c

sin(a-B)cosa-1/2[sin(2a+B)-sinB]=sin(a-B)cosa-1/2[2cos(a+b)sina]=sin(a-b)cosa-cos(a+b)sina=sinacosbc

sin(a+π/6)+cosa=sina*(v3/2)+cosa*(1/2)+cosa=v3[sina*(1/2)+cosa*(v3/2)]=v3sin(a+π/3)=(4/5)*v3,——》sin(

=[(1-cos(a/2))/2]^(1/2)再问：那个，有步骤吗？再答：有一个倍角公式cos2a=(cosa)^2-(sina)^2=1-2*(sina)^2用这个代就好

分子=1-sin^6a-cos^6a=1-（sin^6a+cos^6a）=1-（sin²a+cos²a)(sin^4a-sin^acos6a+cos^4a)=1-(sin^4a-s

sin²(a-π/6)+sin²(a+π/6)-sin²a=(sinacosπ/6-sinπ/6cosa)²+(sinacosπ/6+sinπ/6cosa)&s

1－（sina）^4－（cosa）^4＝［1－（sina）^2］［1＋（sina）^2］－（cosa）^4＝（cosa）^2［1＋（sina）^2］－（cosa）^4＝（cosa）^2［1＋（sina

右边2sin(π/6+A)=2sin(π/6)cosA+2sinAcos(π/6)=cosA+根号3sin(A)=左式.得证#

(1+sina^2+sina^4+sina^6+..+)加到无穷=（1-(sina)^n）/（1-(sina)^2）=1/（1-(sina)^2）=1/(cosa)^2因为sina

得2/3.分母将1化成（sin^2a+cos^2a）^3,分子中的1化成（sin^2a+cos^2a）^2,得到式子等于(2sin^2acos^2a)/(3sin^2acos^2a(sin^2a+co

令x=(sina)^2,则(cosa)^2=1-x.所以原式=x^4-(1-x)^4-x^3+(1-x)^3+x^2=[x^2+(1-x)^2][x^2-(1-x)^2]-x^3+(1-3x+3x^2

分子=1-sin^6a-cos^6a=1-（sin^6a+cos^6a）=1-（sin^a+cos^a)(sin^4a-sin^acos6a+cos^4a)=1-(sin^4a-sin^acos^a+

已知sin(a+π/4)=√6/3所以cos(2a+π/2)=1-2sin²(a+π/4)=1-2*(√6/3)²=-1/3所以sin2a=1/3所以tana+cota=sina/

cos(a-π/6)+sina=4√3/5=>sin(a+π/6)=4/5∴cos(a+π/6)=±3/5sin(a-7π/6+π/6-π/6)=sin(a+π/6-4π/3)=sin(a+π/6)c

是不是sin^2a+cos^2(π/6+a)+1/2sin(2a+π/6)=(1-cos2a)/2+(1+cos(π/3+2a))/2+1/2sin(2a+π/6)=1-1/2cos2a+1/4cos

2sin(a/2)=cos(a/2）tan(a/2)=1/2sinα=2tan(α/2)/[1+tan^2(α/2)]=1/（1+1/4）=4/5cosα=[1-tan^2(α/2)]/[1+tan^