tana是方程x^2+2xseca+1=0的2根中较小的根设另一根为x1则：x1*tana=1x1=cota所以：tana+cota=-2seca(sin^2 a+cos^2 a)/sinacosa=-2seca1/sinacosa=-2/cosasina=-1/2a=2kπ-π/6,或,a=2kπ-5π/6因为：tana...