Create Radius with Polygon Cut

Important points.

Do not pick points along the Arch to do a polygon cut.

Select Extreme end of the Arc and Create tangent to circle at those points.

Use the intersection of the tangents as one polygon cut node.

Other nodes should be outside the Arc.

No node of the Polygon should be on the Arc.

2 Nodes on the tangent outside the arc.

1 Node on the Tangent intersction

4th Node to close the polygon as needs to be.

The video says any point on the arc. Any point will not do- extreme points of the arc is necessary