Answer:
He's half right.
Explanation:
So far so good. You will have the length of the base where it belongs and correct. The problem is that you are not finished. How does he suggest you draw the other two lines?
One way is to draw the perpendicular bisector to the from the midpoint of the base line. The perpendicular bisector is sqrt(3)/2 * the length of the base.
He's about 1/2 right.