求值：cos^2 1度+cos^2 2度+…+cos^2 180度=___.

求值：cos^2 1度+cos^2 2度+…+cos^2 180度=___. 2cos^2 22.5 - 1求值 求值Cos pai/17 *cos 2pai/17*cos 4pai/17*cos 8pai/17 cos^1度+cos^2度+cos^3度+……+cos^180度=? 化简sin(π-a)tan(2π-a)cos(-a+3π/2)/tan(-π-a)cos(-π-a)（1）若cos(a+2π)=1/5求值（2）a=-1860度，求值 求值：cos^2α-sin^2α cos(3π/2 - π/3),求值 求值:cos(arcsin√3/2)= 求值cos(arcsin3/5+2arctan2) 求值∫dx/(cos^2 x) 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) 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[1/cos^2(80°)-3/cos^2(10°)]1/cos20° sin(π+π/6)-cos(π+π/4)cos(-π/2)+1求值 求值cos^2a+cos^2(a+120°)+cos^2(a+240°) 求值：cos²A+cos²（2π/3+A)+cos²(2π/3-A)