What small part of the circumference of circle 1 (Diagram [25].) is marked?
It is called an “arc.”
An arc is any part of a circumference.
Read five arcs that are marked.
Which is longer, the arc e d, or the arc e f? b d, or b d e? a b d, or a b d e?
Name an arc which is half of the circumference.
It is called a “semi-circumference.”
“Semi” means “half.”
A semi-circumference is half of a circumference.
Read three arcs, each of which is one-fourth of the circumference.