Is upside down triangle also polygon

Yes because its is the same thing with a different view

An upside-down triangle is a polygon. A polygon is a figure with at least three straight sides or angles. A triangle has three sides, so it would be classified as a polygon.

Your question asks if an upside-down triangle is a polygon. It is, because it is just upside-down, it is still a triangle. The placement of the shape or the way the shape is facing does not effect it's classification as a polygon.