1.
If limx0[1+xlog(1+b2)]1/x=2bsin2θ\displaystyle\lim_{x\to0}[1+x\log(1+b^2)]^{1/x}=2b\sin^2\theta, b>0b>0 and θ(π,π]\theta\in(-\pi,\pi], then the value of θ\theta is