As part of constructing an isosceles triangle, Gail drew a line segment and plotted one vertex of the triangle on the line segment. With this vertex as the center, Gail drew an arc to create a 180 degree angle. How can Gail ensure that the two other points she plots will be the remaining two vertices of an isosceles triangle?
Construct a perpendicular line and plot one point on the perpendicular line and the other inside the arc.
Plot both the points on the arc.
Plot both the points on the line segment.
Plot one point on the arc and the other beyond the arc.

Question

As part of constructing an isosceles triangle, Gail drew a line segment and plotted one vertex of the triangle on the line segment. With this vertex as the center, Gail drew an arc to create a 180 degree angle. How can Gail ensure that the two other points she plots will be the remaining two vertices of an isosceles triangle? 
 Construct a perpendicular line and plot one point on the perpendicular line and the other inside the arc. 
 Plot both the points on the arc. 
 Plot both the points on the line segment. 
 Plot one point on the arc and the other beyond the arc.