t=cosθ
(1-t^2+4)/(t+1)=2 ==>5-t^2=2t+2 ==>t^2+2t-3=0 ==>(t+3)(t-1)=0 ==>t=1 ==>sinθ=0
（cosθ+3）（sinθ+1）=(1+3)(0+1)=4