双曲线x^2/9-y^2/16=1的渐近线是直线y=±4x/3,其斜率是tanA=±4/3.
tan2A=2tanA/[1-(tanA)^2]
=2(4/3)/(1-16/9)=-24/7
--->夹角(锐角)为arctan(24/7).