The formula to find the circumference of a circle given the information we know (the diameter), you could use the circumference formula of c=pi*diameter or: c=3.14 * 4 c=12.56 is the circumference IF THE CIRCLE WAS WHOLE, but since we're working with a semicircle (and in this case, what looks to be exactly 1/2 of a circle), you could divide 12.56 by 2 and come up with 6.28 as the circumference of each of the semicircles.
From the diagram/figure; Line EF is perpendicular to both lines AB and CD Line AB and lines CD are parallel to each other Line GH is neither parallel nor perpendicular to any line given.
