求化简cos(2a+π/4)

求化简cos(2a+π/4) 1-sin2a-cos^2(a-π/4) 化简(2cos^2A-1)/2tan(π/4-A)cos^2(π/4-A) 已知cosa=1/4,求sin(2π+a)cos(-π+a)/cos(-a)tana 化简 1-sin^4a-cos^4a/cos^2a-cos^4a 化简(1-sin^6 a-cos^6 a)/(cos^2 a-cos^4 a)== cos^2(π/3-a)+cos^2(π/6+a) 化简 cot(a+4π)cos(a+π)[sin(a+3π)]^2/tan(π+a)[cos(-π-a)]^2 证明sin(4A)sin(2A)(1-cos(2A)) cos(4A)cos(2A)(1 cos(2A))=cos(2A 急：：已知sin(3π+a)=2cos(a-4π),求(5sin(π/2+a)+cos(π/2-a))/(2cos(π+ 化简：(4cos^4a-4cos^2+1)/[2tan(π/4-a)sin^2(π/4+a)] 已知tan(4分之π+a)=二分之一.求(sina·cosa-cos^2a)/2cos^2a