化简：sin^2a*tana+cos^2a/tana+2sina*cosa

化简sin²a*tana+cos²acota+2sinacosa 化简：sin^2a*tana+cos^2a/tana+2sina*cosa 证明cos^4 a-sin^4 a=cos^2(1-tana)(1+tana) 证明sin^4 a+cos^4 a=cos^2(1-tana)(1+tana) tana=2,求sin^2a-cos^2a tana=2 sin^a+2cos^2a=? (cota-tana)/(sin^2a-cos^2a)+(seca/sina)化简（cota-tana）/(sin^2a-cos^2a)+(seca/sina) 化简1.（sina-cosa）² 2.sin a/2cos a/2 3.cos四次方a -sin四次方a 4.1/1-tana -1/1+tana [3sin^2 (a/2)-2sin(a/2)cos(a/2)+cos^2 (a/2)]/[tana+1/tana] 求证sin^2a*tana+cos^2a*1/tana+2sina*cosa=tana+1/tana 化简[tan(-a-π)*sin(2π+a)]/[cos(-a)*tana] (sin(-a-π)-tan(-a)+cot(π/2+a))/((tana-π)+cos(π-a)+sin((3π)/2+a)) 化简 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. (1-2sinAcosA)/(cos^2A-sin^2A)=(1-tanA)/(1+tanA) 证明(1-2sinAcosA)/(cos^2A-sin^2A)=(1-tanA)/(1+tanA) 求证：(1-tana)/(1+tana)=(1-2sinacosa)/(cos^2×a-sin^2×a) cos^2a-sin^2a/1+2sinacosa=1-tana/1+tana怎么证明?