What is the area of the marked region?



The marked region is an isosceles triangle with two sides with length \(\dfrac{1}{2}\) and one side with length \(\dfrac{\sqrt{3}}{2}\), see and .
Hence its area equals \[\dfrac{\sqrt{3}}{4}\cdot\sqrt{\dfrac{1}{4} - \dfrac{1}{16}} = \dfrac{3}{16}\,.\]