Вычислите $$\frac{sin^2765^\circ}{1-cos420^\circ}$$

$$\frac{sin^2765^\circ}{1-cos420^\circ}$$$$=\frac{sin^245^\circ}{1-cos60^\circ}=\frac{\left(\frac{\sqrt2}2\right)^2}{1-\frac12}=\frac{\frac24}{\frac12}=1$$