求证sin^2A+cos^2A=1tanA=sinA除以cosA

求证：tan a/2＝(1-cos)/sin a=sin a/(cos a+1) 求证 cos^2 a-sin^2 a/1-2sin acos a =1+tan a/1-tan a 求证3-sin^4a-cos^4a/2cos^a=1+tan^a+sin^a 速答 谢谢 求证：sin^2A+cos^2A+sinAcosA/sin^2A+cos^2A=tan^2A+1+tanA/tan^2A+1 求证1/（sin^2)a+1/(cos^2)a-1/(tan^2)a=2+(tan^2)a 求证：1/sin²a+1/cos²a-1/tan²a=2+tan²a 为什么 tan a +1/tan a=sin^2 a +cos^2 a/(sina cos a) 求证 sin~4a-cos~4a=sin~2a-cos~2a tan~2asin~2a=tan~2a-sin~2a 求证:sin a(1+tan a)+cos a(1+1/tan a)=1/sin a+1/cos a 求证:sin^2/(sin-cos) - (sin+cos)/(tan^2 -1) =sin+cos 证明tan a/2=sin a/(1+cos a) 求证:2sin(a-3π/2)cos(a+π/2)-1/1-2sin^(π+a)=tan(9π+a)+1/tan(π+a)-1 sin(2a)[cot(a/2)-tan(a/2)]=4cos^2(a)求证, 求证1+sin a+cos a+2sin acos a/1+sin a+cos a=sin a+cos a sin 2a+2sin方a/ 1+tan a =2sin a cos a 求证[1]1-2sin acos a/cos²a -sin²a =1-tan a/1+tan a.[2]1-cos 2θ/1+cos 2θ=tan²θ tan a/2=sin/1+cos a=1-cos a/sin a 求证:sin 2a/1+sin a+cos a=sin a+cos a-1急