Exercise 9 Page 524

First, we place the compass at $A.$ Using a compass setting that is greater than half the length of $\overline{AB},$ we draw an arc.

Keeping that same compass setting, we draw one more arc. This time we place the compass at $B.$ We draw the second arc so that it intersects the first one at two points.

Finally, we draw a line through the points of intersection. This line is the perpendicular bisector to $\overline{AB}.$ It passes through $M,$ the midpoint of $\overline{AB}$ so $AM=MB.$

Let's show the finished product.