[RESOLVED] question on Constructible polygon

[Harsh Gupta]

please see this image
could anyone explain how (talking about the first figure for equilateral triangles) it signifies an equilateral triangle??

thank you

[Andy_P]

The line OB needs to be extended.

Check this pic instead:

[Harsh Gupta]

ok, but then how would i mark this point D in the semi-circle?

[Andy_P]

Point D is the mid point of line OB.

[Harsh Gupta]

aha, thank you

[Andy_P]

Just as a note, the two small check marks on lines BD and OD denote that they are of equal length.