It is proved that the arcs added by two parallel strings of a circle are equal

It is proved that the arcs added by two parallel strings of a circle are equal

Bisecting the string perpendicular to its diameter and bisecting the two arcs of the string. (theorem)
Should I have learned this theorem?
1. Any diameter divides the circle into two arcs of equal length
2. (theorem) = & gt; two arcs corresponding to two parallel strings are bisected respectively perpendicular to the diameter of the string
1 & amp; 2 = & gt; "two strings bisected by diameter" minus "two arcs corresponding to two parallel strings bisected by diameter" equals the remaining arcs, that is, the arcs between two parallel strings of a circle must be equal
complete
It's better to add letters when proving