cos^2x-sin^2x=cos(2x)=1/2解有x=2kπ±π／3,k∈Z故当k=-2时x1=-11π/6当k=-1时x2=-7π/6,x3=-5π/6当k=0时x4=-π/6,x5=π/6当k=1时x6=5π/6,x7=7π/6当k=2时x8=11π/6所以x在[-2π,2π]上所有解的和：x1+x2+x3+x4+...