cos(-7 π /4)
【紧急求助】计算:cosα+cos(2π/3 +α)+cos(4π/3 +α)
化简sin(2π+a)cos(π-a)cos(π/2-a)cos(7π/2-a)/cos(π-a)sin(3π-a)si
求值:cos(25π /4)
不用计算器,求(cos(π/8))^4+(cos(3π/8))^4+(cos(5π/8))^4+(cos(7π/8))^
已知cos(π4
化简cos(π/12)*cos(5π/12)
cos(- 19/4 π)=?
cos^2(π/6)
计算cos(a+5π/12)cos(a+π/6)+cos(π/12-a)cos(π/3-a)
求值:sin(π/4+3x)cos(3/π-3x)+cos(π/6+3x)cos(π/4+3x)
帮我解,证明恒等式(cos平方5π/12)+(cos平方π/12)+(cos5π/12)(cosπ/12)=5/4
1.化简f(x)=cosx(asinx-cosx)+cos(π/2-x)cos(π/2-x).2.化简f(x)=4cos