This is the concept of geometry, the total sum of angles in a hexagon is given by:
(n-2)*180
=(6-2)*180
=720
the size of each interior angle will be:
120°
N/B
the exterior and interior angles are supplementary to each other.
Therefore the size of the exterior angle will be:
180-120
=60°
the answer is A
Side a = 10.98991
Side b = 11.69522
Side c = 4
Angle ∠A = 70° = 1.22173 rad = 7/18π
Angle ∠B = 90° = 1.5708 rad = π/2
Angle ∠C = 20° = 0.34907 rad = π/9