sin a +cos a =1/2 0

证明Cos^A-Sin^A=1-2Sin^A=2Cos^A-1=cos^a-sin^a tan a/2=sin/1+cos a=1-cos a/sin a 求证：tan a/2＝(1-cos)/sin a=sin a/(cos a+1) 已知 sin a-cos a=1/2,则 sin^3 a-cos^3 a 化简(1-sin^6 a-cos^6 a)/(cos^2 a-cos^4 a)== 证明sin(4A)sin(2A)(1-cos(2A)) cos(4A)cos(2A)(1 cos(2A))=cos(2A 若sin^4a/sin^2b+cos^4a/cos^2b=1,证明sin^4b/sin^2a+cos^4b/cos^2a 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)\( 为什么 tan a +1/tan a=sin^2 a +cos^2 a/(sina cos a) 已知sin a-2cos a=0 求4sin^2 a-3sin a x cos a-5cos^2 a的值 已知tan a=2,求(1)(sin a-3cos a)/(sin a+cos a) (2)(2sin^2 a-3cos