lim(x→π)sinmx/sinnxx=π-tlim(x→π)sinmx/sinnx=lim(t→0)sinm(π-t)/sinn(π-t)=lim(t→0)[-mcos(m(π-t))]/[-ncosn(π-t)]m和n同时为奇数或同时为偶数时，lim(x→π)sinmx/sinnx=m/nm为奇数n为偶数，或者m为偶数n为奇数时，lim(x→π)sinmx/sinnx=-m/n
