设直线y=4/3x+1的倾斜角的一半为θ;则tan2θ=4/3;→2tanθ/(1-tan^2 θ)=4/3;→3tanθ=2-2·tan^2 θ;2·tan^2 θ +3tanθ -2 =0;解得:tanθ=-2(舍);tanθ=1/2.则所求方程为:y-3=tanθ·(x+2)即y=(1/2)x +4.choose B...