A raing is a roond set, sic as the letter "o". It is the set generate bi a pynt tracin oot a peth that's aye a fixt lenth (the radius, r) frae some ither fixt pynt (the mids).
The diameter ("aa the wey athort"), or d, o a raing is equal tae its radius twice ower, i.e. d=2r)
The nummer pi, for ordinar written uisin its seembol π, equal tae aboot 22/7 or 3.14159, is gey uissfu whan dealin wi raings:
- The circumference ("aa the wey aboot") o a raing (c) is equal tae π tymes the diameter (c=πd).
- The area o a raing (a) is equal tae the radius quadert , syne multiplee'd bi π (a=πr ²).