如果cos(兀+a)=-1/2,那sin(兀/2+a)=

如果cos(兀+a)=-1/2,那sin(兀/2+a)= 证明Cos^A-Sin^A=1-2Sin^A=2Cos^A-1=cos^a-sin^a 已知a(-0,兀且2SIN A-SIN ACOS A-3COS A=0求SIN(+兀/4)/SIN 2A+COS 2A+ 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sin(兀+a)cos(3/2兀+a)+sin(兀/2+a)cos(兀+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 已知a属于（0,π/2）,且2sin^2 a-sin a cos a-3cos^2 a=0,求SIN(a+兀/4)/SI 证明tan a/2=sin a/(1+cos a)