√(1-sin 38°) = cos 19° - sin 19°

√(1-sin 38°) = cos 19° - sin 19° 求证:sin^2/(sin-cos) - (sin+cos)/(tan^2 -1) =sin+cos sin^2 30°+cos()=1 sin^4+cos^4=1,求sin+cos= [1+cos.sin]/{cos+sin}的值域 化简 （1+sin a+ cos a)(sin a/2 - cos a/2) / √(2+2cos a)(180° 求证1+sin a+cos a+2sin acos a/1+sin a+cos a=sin a+cos a 求证1/sin^2a+3/cos^2a>=4+2根号下31/sin²a +3/cos²a=(sin²a+cos²a)/sin²a +3(sin²a+cos²a)/cos²a=1+cos²a/sin²a+3+3sin²a/cos²a=4+cos²a/sin²a+3sin²a/cos²a≥4+2√[(cos 已知α为第二象限角,化简cosα√（1-sinα/1+sinα)+sinα√(1-cosα/1+cosα)求证：1+sinα+cosα+2sinαcosα/1+sinα+cosα=sinα+cosα 请会的大哥大姐多多指教.已知sinθ=(√5-1)/4(1)求(sinθ-cosθ)/(sinθ+cosθ)+(sinθ+cosθ)/(sinθ-cosθ)的值.(2)已知5sinθ+12cosθ=0,求(sinθ+9cosθ)/2(2-3sinθ)的值. 求证:sin 2a/1+sin a+cos a=sin a+cos a-1急 求证sinθ/(1+cosθ)+(1+cosθ)/sinθ=2/sinθ 求证:sinα/(1+cosα)+(1+cosα)/sinα=2/sinα 已知α=7/12π,那么cosα√（1-sinα）/(1+sinα)+sinα√（1-cosα）/(1-cosα)= sinα=-2cosα,求sin^2α-3sinαcosα+1 若sinαsinβ+cosαcosβ=0,则sinαcosα+sinβcosβ= .1若sinαsinβ+cosαcosβ=0,则sinαcosα+sinβcosβ= 2已知sin(α+β)=1,则cos(α+2β)+sin(2α+β)=急, cos^6(π/8)-sin^6(π/8)=求值,[cos^2(π/8)-sin^2(π/8)][cos^4(π/8)+sin^4(π/8)+cos^2(π/8)sin^2(π/8)]=cos(π/4)[1-cos^2(π/8)sin^2(π/8)]=cos(π/4)[1-[sin^2(π/4)]/4]==7√2/16 已知sin[a-b]cos a-cos[b-a]sin a=3/5,b是第三象限角,求sin[b+5π/4]的值第一题1/2cos x-√3/2sin x第二题√3sin x+cos x第三题√2[sin x-cos x]第四题√2cos x-√6sin x