设α,β,y∈R,则sinα+siny=sinβ,cosα+cosy=cosβ,则α-β

设α,β,y∈R,则sinα+siny=sinβ,cosα+cosy=cosβ,则α-β 三道三角函数的题目1.设tan1234°= α,则sin(-206°) + cos(-206°) 等于多少?(用α表示)2.已知sinβ = 1/3 ,sin(α+β) = 1 ,则sin(2α+β)等于多少?3.已知sinx + siny = 1/2 ,则siny - (cosx)^2的最大值为多少? 存在一对x,y属于R,sin(x-y)=sinx-siny是真命题么? 已知sinα+sinβ+siny=0,cosα+cosβ+cosy=0,求cos（β-y）的值 设α,β∈R,A(cosα,sinα),B(cosβ,sinβ),则|AB|max= 证明sin(x+y)sin(x-y)=sinx-siny 证明sinx+cos(x+y)siny/cosx-sin(x+y)siny=tan(x+y) 已知sinα+sinX+sinY=0,cosα+cosX+cosY=0,则cos（X-Y） 求思路过程.跪谢 已知sinα +sinβ+ siny=0,cosα +cosβ +cosy=0,求cos(α-β) 若cos(x+y)cosy+sin(x+y)siny=0,则cosx= sinx+cosy=1/3 cosx+siny=1/6 则sin(x+y)=?RT sinx+cosy=1/3 cosx+siny=1/6 则 sin(x+y)? 设y=x+siny,则[(d^2)y]/[dx^2]=? 为什么sinx*cosy-cosx*siny=sin(x-y) 求函数z=sinx+siny+sin(x+y)(0 存在sin( x -y) = sinX-sinY吗 (sinx-siny)/sin(x+y) = sin1/2(x-y)/sin1/2(x+y)还有这个sec(π/4+α)sec(π/4-α)=2sec2α 一道三角函数题,若sin(x-y)cosy+cos(x-y)siny≥1,则x,y的取值范围分别是?（答案是x=2kπ+2分之π,k属于z,y属于R