求证：(cosa-1)^2+sin^2a=2-2cosa

求证：(cosa-1)^2+sin^2a=2-2cosa 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sin(3π/2-a)=-cosa 求证sin(3π/2+a)=-cosa 求证：sin(3/2π+a)=-cosa 求证1+2sina cosa/sin^2a-cos^2a=tana+1/tana-1 求证：1+2sina cosa /sin^2a -cos^2a = tana +1/tana -1. 求证2(1+cosa)-sin∧2a=4cos∧4a/2 求证sin^2A+cos^2A=1tanA=sinA除以cosA 求证：cosa(cosa-cosb)+sina(sina-sinb)=2sin^2a-b/2 求证：1加cosA加2sin平方A／2等于2 求证:sin的平方a/4=(1-cosa/2)/2 求证2sina+sin2a=2sin^3a/(1-cosa) 求证：cosA°sinB°=1/2【sin（A+B）°-sin（A－B）°】 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(a+β)sin(a-β）=（cosβ）^2-(cosa)^2 三角函数恒等式求证：cosa + sina / cosa - sina + cosa - sina / cosa + sina = cos＾2a - sin＾2a / 2