求证3-sin^4a-cos^4a/2cos^a=1+tan^a+sin^a 速答 谢谢

求证：tan a/2＝(1-cos)/sin a=sin a/(cos a+1) 已知tan a=-1/3,求4sin a-2cos a/5cos a+3sin a= 求证:sin a(1+tan a)+cos a(1+1/tan a)=1/sin a+1/cos a 已知tan a=2,求:(4*sin a-2*cos a)/(5*sin a+3*cos a)的值 求证[1]1-2sin acos a/cos²a -sin²a =1-tan a/1+tan a.[ 证明:cos^4 a-sin^4 a=cos^2 a(1-tan a)(1+ tan a) 证明恒等式tan a*sin a/tan a-sin a=1+cos a/sin a 为什么 tan a +1/tan a=sin^2 a +cos^2 a/(sina cos a) tan a/2=sin/1+cos a=1-cos a/sin a 证明tan a/2=sin a/(1+cos a) 已知2cos∧2 a+3cos a sin a-3sin∧2 a=1,求:tan a,(2sin a-3cos a)\( 求证：sin^2A+cos^2A+sinAcosA/sin^2A+cos^2A=tan^2A+1+tanA/tan^2A