A straight edge
Chat with our AI personalities
Place the ruler side by side with the object. One of the edges of the object should be in the "0" value of the ruler. Then just see where the other edge is and there you have it.
An arc (segment of a circle) has one straight side, and one curved side.
By looking at the object straight, instead of from either side?
Is called a straight angle.
That would be a pentagon.