We started with p 65:22 - a problem from a previous unit that asks us to locate several points in the coordinate plane that would make an isosceles triangle with the segment in the book. In other words: several points that are equidistant from the endpoints of segment RY. Connecting 5 of these points allowed us to locate the perpendicular bisector of RY.
What is a perpendicular bisector? A line that passes through the MIDPOINT of a segment at a RIGHT ANGLE. We discussed the difference between this and just a segment bisector (passes thru midpoint at any angle). See good sketches on p 147. We did the investigations on pp 147-8 to discover that points on the perpendicular bisector are equidistant from the endpoints of a segment, AND just like the warm-up: if a point is equidistant from the endpoints of a segment, then it is on the perpendicular bisector. This converse was used to discover the actual construction for perpendicular bisector.
After sharing good homework and measuring our answers for accuracy, we looked at medians on p 149 and made up a definition based on the sketch. None of our definitions or conjectures got written up today.
We then made triangles with a straightedge and practiced constructing perpendicular bisectors of the sides, as well as locating a median after this construction (use perpendicular bisector to find the midpoint, connect back to a vertex of the triangle with a ruler).
HW #12: pp 149-50: 1-4, 7-8
We also viewed tests (except 3rd, which got new seats).
Link to mathopenref is in the post below this one.