1.
lim⁡x→π/21−tan⁡(x/2)1+tan⁡(x/2)⋅1−sin⁡x(π−2x)3\displaystyle\lim_{x\to\pi/2}\frac{1-\tan(x/2)}{1+\tan(x/2)}\cdot\frac{1-\sin x}{(\pi-2x)^3}