若cosA-2sin(A-B)=0,求证:tan(A-B)=cosB/(sinB+2)

若cosA-2sin(A-B)=0,求证:tan(A-B)=cosB/(sinB+2) sin(A-B)=0,求证cos(A-2B)=cosA 求证：sin(a+b)cosa-(1/2)[sin(2a+b)-sinb]=sinb 求证cosa*sinb=1/2[sin(a+b)-sin(a-b)] 求证：cosa(cosa-cosb)+sina(sina-sinb)=2sin^2a-b/2 求证：cosA°sinB°=1/2【sin（A+B）°-sin（A－B）°】 若sina+cosb=1,cosa+sinb=根号2,求证sin(a+b)=1/2 Rt三角形中 角c等于九十度 求证 sin^2A?tanA+sin^2B?tanB=1-2sin^2A?sin^2B/cosA?cosB 求证sin(3π/2-a)=-cosa 求证sin(3π/2+a)=-cosa 求证：sin(3/2π+a)=-cosa 若sin(A+B)sin(B-A)=m,则(cosA)^2-(cosB)^2=? 已知A+b+C=π 求证 cosA+cosB+cosC=1+4sin(A/2)sin(B/2)sin(C/2) 求证：(cosa-1)^2+sin^2a=2-2cosa 求证:sin(a+b)cos(a-b)=sina*cosa+sinb*cosb麻烦个位 帮个忙~ 求证:sin(a+β)sin(a-β）=（cosβ）^2-(cosa)^2 若θ,a为锐角且tanθ=(sina-cosa)/(sina+cosa),求证：sina-cosa=√2sinθ. 已知cosa=cosx*siny,cosb=sinx*siny求证：sin^2a+sin^2b+sin^2y=2