This Shape is a Pentagon. Five sided figure.
There are 5 angles at a point. The sum of the 5 angles is 360.
Let each angle be x.
5*x = 360
x = 360/5
x = 72
The perpendicular divides the central angle 72 into 2 equal parts.
72/2 = 36
Angle 3 + 36 + 90 = 180 Sum of angles in Triangle
Angle 3 + 126 = 180
Angle 3 = 180 - 126
Angle 3 = 54 degrees.