记t=tan(x/2),由万能公式,做代换 　　得sinx=2t/(1+t²),cost=(1-t²)/(1+t²) 　　∴2(1-t²)/(1+t²)=2t/(1+t²)+1 　　=>2(1-t²)=2t+1+t²=>3t²+2t-1=0 　　=>(3t-1)(t+1)=0=>t=1/3或-1 　　即tan(x/2)=1/3或-1 　　∴x/2=arctan(1/3)+kπ或-π/4+kπ,k为任意整数 　　即x=2arctan(1/3)+2kπ或-π/2+2kπ,k为任意整数