there some parts of the solution on the book where i found this problem.

Area of shaded region = A sector + [ A triangle - 2 (A sector 2)]

= 5/6 A circle + [ (s^2 * sqrt of 3)/4 - 2(1/6 A of circle)]

... i understand the 5/6 A circle and the 2(1/6 Area of circle, but i dont understand the (s^2*sqrt of 3)/4 for the Area of triangle.... how was that being done? please help me understand this. Thank you.