?????????? "standing on a given ark" ??????????
wot if me SIT on the serkel???
Me thank wot em talk bout is the dubel angel idea.
Draw a diameter kros serkel (gotta go thru senter).
Tu make it eezee tu understand, draw horizontal line thru senter.
At far left, draw line from left end av diameter tu NE point on the serkel.
This make angel with diameter.
Then draw line from serkel senter tu same point over on the rite side.
Then, angel at senter=2* angel at left end.