sin3a=3sina-4sin3次方a

(4sinA-2cosA)/(5cosA+3sinA)=(4tanA-2)/(5+3tanA)=(4*3-2)/(5+3*3)=5/7(sinA-cosA)^2=1-2sinAcosA=1-sin2A

因为sin3a＝3sina－4sin^3(a)=sina(3-4sin^2a)cos3a＝4cos^3(a)－3cosa=cosα(4cos^2a-3)所以sin3a/sina=3-4sin^2a①c

如图

3sinA+sin3A)/(3cosA+cos3A)=（3sinA+sin(2A+A))/(3cosA+cos(2A+A))=(3sinA+sin2AcosA+cos2AsinA)/(3cosA+co

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

2(sina)^2-sinacosa-3(cosa)^2=0,(2sinα-3)(sinα+1)=0,sinα=-1(sinα=3/2舍去)sin(a+π/4)/(sin2a+cos2a+1)=sin

sin(2A+A)=Sin2AcosA+Cos2ASinA=2sinACos平方A+SinA-2Sin三次方A=sinA(2cos平方A+1)-2sin立方A=sinA(2-2sin平方A+1)-2s

sinA+sin5A=sin(3A-2A)+sin(3A+2A)=2sin3Acos2A同理有sin3A+sin7A=2sin5Acos2A所以原式=（cos2A+1）sin3A/(cos2A+1)s

tana=2（sina）^2=4/5(cosa)^2=1/5（sina）^6+(cosa)^6=[（sina）^2+(cosa)^2][（sina）^4+(cosa)^4-（sina）^2*(cosa

3sina+sin3a)/(3cosa+cos3a)=(6sina-4sin3a)/4cos3a=(3tana/2cos2a)-tan3a=(3tanasec2a/2)-tan3a==[3tana(1

.两角和与差的三角函数sin(a+b)=sin(a)cos(b)+cos(α)sin(b)cos(a+b)=cos(a)cos(b)-sin(a)sin(b)sin(a-b)=sin(a)cos(b)

3sinA+sin3A)/(3cosA+cos3A)=（3sinA+sin(2A+A))/(3cosA+cos(2A+A))=(3sinA+sin2AcosA+cos2AsinA)/(3cosA+co

(sina+cosa)/(sina-cosa)=2=>sina=3cosa,tana=3,(seca)^2=10(3sina+cosa)/(2sina+3cosa)=(3tana+1)/(2tana+

检举3sinA+sin3A)/(3cosA+cos3A)=（3sinA+sin(2A+A))/(3cosA+cos(2A+A))=(3sinA+sin2AcosA+cos2AsinA)/(3cosA+

1、先化简函数,再根据公式即可求出周期：y=(sin²x)²+cos²x=[(1-cos2x)/2]²+(1+cos2x)/2=(3+cos²2x)/

sin(π-a)-cos(π+a)=√2/3sina+cosa=√2/3两边平方得1+2sinacosa=2/9sinacosa=-7/18(1)(sina-cosa)²=1-2sinaco

sin3a=sin(2a)cosa+cos(2a)sina=3sinacos²a-sin³acos3a=cos(2a)cosa-sin(2a)sina=cos²a-3si

sin(3a)=sin(2a+a)=sin(2a)cosa+cos(2a)sina=(2sinacosa)cosa+(1-2sin^a)sina=2sina(1-sin^a)+sina-2sin^3a

因为sinA+cosA=1/2所以(sinA+cosA)^2=1/4展开化简后得:2sinAcosA+1=1/4sinAcosA=-3/81-2sinAcosA=(sinA-cosA)^2=1+3/8

如果是有n项相加的话,应该是a=Pi/n,a趋于0,则对应n趋于无穷.a(sina+sin2a+sin3a+sin4a+...+sinπ)=Pi/n×(sinPi/n+sin2Pi/n+sin3Pi/