Okay, here we have this:
Considering the provided circle and information, we are going to calculate the requested area of the shaded sector, so we obtain the following:
Then we will substitute in the following formula:
Sector Area = r² × θ × π / 360
Replacinig:
Sector Area = (4 units)² × 80° × π / 360
Sector Area = 16 units² × 80° × π / 360
Sector Area = 11.17 units²
Finally we obtain that the sector area is approximately 11.17 units^2.