Elipsau gan ddefnyddio cylchoedd cydganol a hirgylchwr.

Ellipses using concentric circles & the trammel.

Disgrifiad

Siâp crwm caeedig yw elips. Mae dwy ffordd o luniadu elips – y dull Cylchoedd Cydganol a’r Dull Hirgylchwr.



Dull Hirgylchwr



Dull Hirgylchwr





  1. Marciwch yr echelin hwyaf AB yn 120mm a’r echelin leiaf CD yn 80mm.
  2. Gan ddefnyddio stribed papur gydag ymyl syth, marciwch hyd OM i N yn hafal i OC, hanner yr echelin leiaf.
  3. Marciwch ail hyd OM i J yn hafal i hanner yr echelin hwyaf OA.
  4. Gan gadw’r marciau N a J yn eu lle ar eu hechelinau, symudwch yr hirgylchwr o gwmpas a marcio pwyntiau ar y papur i gyd-fynd ag OM (y marc allanol).


Description

An ellipse is a closed curve shape. There are two ways of constructing an ellipse - the Concentric Circle method and the Trammel method.



Concentric Circle method



Trammel method





  1. Draw the major axis AB at 120 mm and minor axis CD at 80 mm.
  2. Using a strip of paper with a straight edge mark off length OM to N equal to OC, half the minor axis.
  3. Mark off a second length OM to J equal to half the major axis OA.
  4. Keeping the marks N and J accurately positioned on their respective axes, move the trammel round and mark off points on the drawing paper to coincide with OM (the outer mark).