1. Do Now: Lesson # 4 The Midpoint Formula
In your notebook, use the “Big Ideas” glossary to define:
midpoint and segment bisector.
2. Do the Exploration Worksheet Front only

2. “Tick Marks” are used to show congruent segments in a diagram
Endpoints
Midpoint
“Tick Marks” are used to show congruent segments in a diagram

4. Other times, we may have to use a formula to find the midpoint.
Sometimes, we can count boxes to find the midpoint of a segment, using the SLOPE.
Other times, we may have to use a formula to find the midpoint.

5. The Midpoint Formula (xm, ym) = x1 + x2 , y1 + y2 2 2
y- values of the endpoints
x- values of the endpoints
(xm, ym) = x1 + x2 , y1 + y2
x- value of the midpoint
y- value of
the midpoint

6. The Midpoint Formula
No matter which point you are looking for, plug in the values that you are given and solve for what’s missing.
xm = x1 + x2 2
ym = y1 + y2 2

7. Let’s try #5
on the back
of your
Exploration Sheet

8. To use the Midpoint Formula:
Identify the given coordinates
Label the points or
Write the “EMPTY” formula
Plug in values you are given
Evaluate
6. Write your answer as a coordinate
(x1, y1)
(x2, y2)
(xm, ym)

9. The Midpoint Formula (example)
The midpoint of TU is M(2,4). One endpoint is
T(1,1). Find the coordinates of endpoint, U.
(xm, ym)
(x1, y1)
xm = x1 + x2 2
ym = y1 + y2 2
2 = 1+ x2 2
4 = 1 + y2 2
3 = x2
7 = y2
(x2, y2) = (3,7)

10. COPY A LINE SEGMENT
Pages

11. Pages

12. midpoint, segment bisector and the midpoint formula
Homework #4:
Big Ideas
Page 8: #3-9 odd
Pages 24-26:# 1, 3-9 odd, odd, 36, 42,46-49.
Make flash cards for:
midpoint, segment bisector and the midpoint formula