当a=3π/4时,sin(a+b)+cos(a+b)+sin(a-b)+cos(a-b)

当a=3π/4时,sin(a+b)+cos(a+b)+sin(a-b)+cos(a-b) 当a=3pai /4时,sin (a+b)+cos (a+b )+sin (a-b)+cos (a-b)等于：A 1 B -更号2/2 C 0 D 更号2/2 由cos(a+b)=cos a cos b-sin a sin b cos(a-b)=cos a cos b+sin a sin b解题设a为锐角,证：1、2分之根3乘cos a + 2分之1乘sin a=cos(6分之π-a)2、cos a-sin a=根号2cos(4分之π+a) 已知α∈（0,π/2)向量a=（cosα+sinα)向量b=(-1/2,√3/2)① 证明向量a+b⊥a-b ② 当|2a+b|=|a-2b|时求 已知f(x)=√2 a sin(x-π/4)+a+b当a＜0时f(x)在[0,π]上的值域为[2,3]求a,b 3 在三角形ABC中,已知（a2+b2）sin（A-B）=（a2-b2）sin(A+B) 求证：ABC是等腰或直角三角形(a^2+b^2)sin(A-B)=(a^2-b^2)sin(A+B),(sin^A+sin^B)sin(A-B)=(sin^A-sin^B)sin(A+B) sin^A*(sin(A+B)-sin(A-B))=sin^B*(sin(A-B)+sin(A+B)) sin^A*2c 已知向量a=(sinx,3/4),b=(cosx,-1).当a‖b时求cos^2x-sin^2x的值 已知向量a=(sinx,3/4),b=(cosx,-1）当a//b时,求(cosx)^2-sin(2x)的值 已知向量a=(cosθ,sinθ),b=(√3,1)①当a垂直b时,求tan2θ②求|a+b|的最大值 a=(cosα,sinα) b=(-1/2,根号3/2) a=(cosα,sinα) b=(-1/2,根号3/2)1.求证向量a+b与a-b垂直2.当两个向量根号3a+b与a-根号3b的模相等时 且α∈（0,π/2) 求角α sin(a+b)=-3/5,sin(b-π/4）=12/13,求cos（a+π/4)值 cos(a+b)cos(a-b)+sin(a+b)sin(a-b)=-3/5,求sin(3π/2+2b) 非线性方程解析解-x0*cos(b)*cos(c)-y0*(-sin(a)*cos(b)*cos(c)-cos(a)*sin(c))-z0*(-cos(a)*cos(b)*cos(c)+sin(a)*sin(c))=0-x0*cos(b)*sin(c)-y0*(-sin(a)*cos(b)*sin(c)+cos(a)*cos(c))-z0*(-cos(a)*cos(b)*sin(c)-sin(a)*cos(c))=0 -x0*cos(b)-y0*sin(a)*co sin(A+B)=4/5,sin(A-B)=-3/5,则tanA/tanB= sin(a+b)=1/4,sin(a-b)= 1/3,则tana/tanb等于? sin(π/4-a)=3/5,sin(π/4+b)=12/13,其中0 已知平面向量a=(cosα,sinα),b=(cosβ,sinβ),若a=入b,则实数入的值为?=co, 当a∈(0,π/2)时,求证sin a