向量a(cos二分之三,sin二分之三-搜答案-智慧作业帮

∵sin(2π-A)=√2cos(3π/2-B)=-sinA=-√2sinB∴sinA=√2sinB∵√3cosA=-√2cos(π-B)=√2cosB∴√3cosA=√2cosB又∵sin²

a=(cos(3x/2),sin(3x/2))b=(cos(x/2),-sin(x/2))因此,a·b=cos(3x/2)cos(x/2)-sin(3x/2)sin(x/2)=cos(3x/2+x/2

A=-pi/6+2Kpi或-5pi/6+2kpicos(二分之三派-A)=-√3/2或0

a=(cosα,sinα)(0≤α≤2π),b=(-1/2,√3/2)(a+b)(a-b)=a^2-b^2=1-(1/4+3/4)=0所以,(a+b)⊥(a-b)

sin二分之π,cos二分之π,tan二分之π不是等于1,0,∅

√3sinx/2+cosx/2=y/cosx/2=1/cosx/2则√3sinx/2cosx/2+cos²x/2=1√3/2sinx+1/2(cosx+1)=1sin(x+π/6）=1/2,

√3sinx/2+cosx/2=2(√3/2sinx/2+1/2cosx/2)=2sin(x/2+π/6)3/2cosx-√3/2sinx=√3(√3/2cosx-1/2sinx)=√3cos(x+π

(1)f(α)=sin(α-3π)cos(2π-α)sin(-α+3π/2)/[cos(-π-α)sin(-π-α)]=(-sinα)cosα(-cosα)/[-cosαsinα]=-cosα.(2)

sin二分之A-cos二分之A=五分之一,(sinA/2-cosA/2)^2=1/25,(sinA/2)^2+(cosA/2)^2-2sinA/2cosA/2=1/25,1-sinA=1/25,sin

√2cos(a)/2+√2sin(a)/2=sinπ/4cos(a)+cosπ/4sin(a)=sin(a+π/4).

五分之二倍根号五五分之根号五四十五度

只要清楚两个角互余,也就是和为90度,那么那么他俩的正余弦,正余切相反,例如sin30=cos60 tan30=ctan60还有就是所谓奇变偶不变是指符号,加几个180,比如si

sina/2+cosa/2=1/2两边平方得sin²a/2+cos²a/2+2sina/2cosa/2=1/41+sina=1/4sina=-3/4cos2a=1-2sin

sinα=(sinα/2+cosα/2)^2-1=4/3-1=1/3,cos2α=1-2(sinα)^2=7/9.

二分之一sin15度减二分之根号三cos15度=sin15cos60-cos15sin60=sin(15-60)=sin(-45)=-根号2/2

0.5,也就是1/2

cos(3π/2-A)=cos(3π/2-A-2π)=cos(-A-π/2)=sin[π/2-(-A-π/2)]=sin(π+A)=1/2

sin二分之A乘以COS二分之A=0.5*2sin二分之A乘以COS二分之A=0.5*sinA

平方上面的式子有[cos（a/2）]^2+2cos(a/2)*sin(a/2)+[sin(a/2)]^2=5/4所以2cos(a/2)*sin(a/2)=sina=5/4-1=1/4又cos2a=1-

(1).向量a•向量b=cos(3x/2)cos(x/2)-sin(3x/2)sin(x/2)=cos2x|向量a+b|=[cos(3x/2)+cos(x/2)]^2+[sin(3x/2)