求值(2-4cos^212度)/[csc12度(3-根号3tan12度)]

求值(2-4cos^212度)/[csc12度(3-根号3tan12度)] sin(x+30)*cos(x+45)求值:sin(x+30度)*cos(x+45度)*csc(45度-x)*tg(60度+x)*tg(30度-x)*sec(60度-x)x没给! 求值Cos pai/17 *cos 2pai/17*cos 4pai/17*cos 8pai/17 求值:cos(π/11)cos(2π/11)cos(3π/11)cos(4π/11)cos(5π/11) 求值：cos(π/11)-cos(2π/11)+cos(3π/11)-cos(4π/11)+cos(5π/11) 求值：cos^2 1度+cos^2 2度+…+cos^2 180度=___. 化简求值cos(π/7)cos(2π/7)cos(4π/7) 求值:cos(2pai/7)+cos(4pai/7)+cos(6pai/7)pai打不出,不好意思 求证:cos^8x-sin^8x-cos2x = 1/8(cos6x - cos2x)还有，csc^4a(1-cos^4a)-2cot^2a sin^2 a/sec^2-1 +cos^2 a/csc^2-1+cos^acsc^a 化简[(secα-cosα)*(cscα-sinα)]/2sinα*cosα 求值（根号3tan12°-3）/[sin12°(4cos^212°-2)] 求值：（根号3tan12°-3)/(4cos^212°-2sin12°） cos(pai/15)×cos(2pai/15)×cos(3pai/15)×cos(4pai/15)×cos(5pai/15)×cos(6pai/15)×cos(7pai/15)求值 cos(pai/15)×cos(2pai/15)×cos(3pai/15)×cos(4pai/15)×cos(5pai/15)×cos(6pai/15)×cos(7pai/15)求值 求值： 2(sin^6 θ+cos^6 θ)-3(sin^4 θ+cos^4 θ) sin(π+π/6)-cos(π+π/4)cos(-π/2)+1求值 sinx=根号3/2 90〈X〈180度 求 cos x ,tan x ,cot x,sec x,csc x 等于多少