sin(a/2)-cos(a/2)=-根号5/5 且450

求证1+sin a+cos a+2sin acos a/1+sin a+cos a=sin a+cos a 求证:sin 2a/1+sin a+cos a=sin a+cos a-1急 由cos(a+b)=cos a cos b-sin a sin b cos(a-b)=cos a cos b+sin a sin b解题设a为锐角,证：1、2分之根3乘cos a + 2分之1乘sin a=cos(6分之π-a)2、cos a-sin a=根号2cos(4分之π+a) sin^4+sin^2cos^2+cos^2a= 一个简单的三角函数题(sin a + cos a)/(sin a - cos a) 则 sin a *cos a=(sin a + cos a)/(sin a - cos a) = 2 则 sin a *cos a= 证明Cos^A-Sin^A=1-2Sin^A=2Cos^A-1=cos^a-sin^a cos^2a+sin^2a=? sin^2A/cos^2A=? 求证 1+sin a+cos a+2sin a*cos a/1 +sin a +cos a = sin a+ cos a 有什么思路! 已知a为锐角,且sin a+cos a=根5/2,求sin a*cos a的值 tan a=2,(3sin a-cos a)/(2sin a+cos a)= 已知tan a=2,求sin a+cos a /cos a -sin a 的值 已知tan(a)=3,求sin^2(a)+2sin(a)cos(a)+3cos^2(a)/sin(a)cos(a)+cos^2(a)的值 sin 2a+2sin方a/ 1+tan a =2sin a cos a sin^4a-cos^4a=sin^2a-cos^2a 证明sin^4a-cos^4a=sin^2a-cos^2a sin^6 a＋cos^6 a＋3×sin^2 a×cos^2 a=? tan a/2=sin/1+cos a=1-cos a/sin a