cos(兀-2a)/sin(a-兀/4)=-√2/2
已知(4sin a-2cos a)/(5cos a +3sin a)=6/11,求cos^4 a-sin^4 a
已知a(-0,兀且2SIN A-SIN ACOS A-3COS A=0求SIN(+兀/4)/SIN 2A+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
已知sin a =2cos a .求sin a -4cos a ╱5sin a +2cos a的
已知a是第三象限角,f(a)=sin(兀-a)cos(2兀-a)tan(-a+兀)/sin(-兀-a)tan(-兀-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
(cos a)^4+(sin a)^2*(sin a)^2+(sin a)^2=?
已知tan a=2 求(2sin a-3cos a)/(4sin a-9cos a)
证明Cos^A-Sin^A=1-2Sin^A=2Cos^A-1=cos^a-sin^a