1. Holt McDougal Geometry 1-6 Midpoint and Distance in the Coordinate Plane 1-6 Midpoint and Distance in the Coordinate Plane Holt Geometry Warm Up Warm Up Lesson Presentation Lesson Presentation Lesson Quiz Lesson Quiz Holt McDougal Geometry

2. 1-6 Midpoint and Distance in the Coordinate Plane Warm Up 1. Graph A (–2, 3) and B (1, 0). 2. Find CD. 8 3. Find the coordinate of the midpoint of CD. –2 4. Simplify. 4

3. Holt McDougal Geometry 1-6 Midpoint and Distance in the Coordinate Plane Develop and apply the formula for midpoint. Use the Distance Formula and the Pythagorean Theorem to find the distance between two points. Objectives

4. Holt McDougal Geometry 1-6 Midpoint and Distance in the Coordinate Plane Coordinate Plane x-axis y-axis origin -5 2 How do we find that midpoint of the segment above?

5. Holt McDougal Geometry 1-6 Midpoint and Distance in the Coordinate Plane You can find the midpoint of a segment by using the coordinates of its endpoints. Calculate the average of the x-coordinates and the average of the y-coordinates of the endpoints.

6. Holt McDougal Geometry 1-6 Midpoint and Distance in the Coordinate Plane Average of the x coordinates Average of the y coordinates

7. Holt McDougal Geometry 1-6 Midpoint and Distance in the Coordinate Plane Example 1: 1) Find the coordinates of the midpoint of PQ with endpoints P(–8, 3) and Q(–2, 7). = (–5, 5)

8. Holt McDougal Geometry 1-6 Midpoint and Distance in the Coordinate Plane 2) Find the coordinates of the midpoint of EF with endpoints E(–2, 3) and F(5, –3). Example 2:

9. Holt McDougal Geometry 1-6 Midpoint and Distance in the Coordinate Plane Example 3: M is the midpoint of XY. X has coordinates (2, 7) and M has coordinates (6, 1). Find the coordinates of Y. Step 1 Let the coordinates of Y equal (x, y). Step 2 Use the Midpoint Formula:

10. Holt McDougal Geometry 1-6 Midpoint and Distance in the Coordinate Plane Example 3 Continued Find B’s the x-coordinate. Set the coordinates equal. Multiply both sides by 2 to get rid of the denominator. 12 = 2 + x – 2 10 = x 2 = 7 + y – 7 –5 = y The coordinates of Y are (10, –5). Find B’s the y-coordinate.

11. Holt McDougal Geometry 1-6 Midpoint and Distance in the Coordinate Plane Example 4 S is the midpoint of RT. R has coordinates (–6, –1), and S has coordinates (–1, 1). Find the coordinates of T. Step 1 Let the coordinates of T equal (x, y). Step 2 Use the Midpoint Formula:

12. Holt McDougal Geometry 1-6 Midpoint and Distance in the Coordinate Plane Example 4 Continued Step 3 Find the x-coordinate. Set the coordinates equal. Multiply both sides by 2. –2 = –6 + x Simplify. + 6 4 = x Add. Simplify. 2 = –1 + y + 1 3 = y The coordinates of T are (4, 3).

13. Holt McDougal Geometry 1-6 Midpoint and Distance in the Coordinate Plane The Distance Formula is used to calculate the distance between two points in a coordinate plane.

14. Holt McDougal Geometry 1-6 Midpoint and Distance in the Coordinate Plane Example 5: Find FG and JK. Then determine whether FG  JK. Step 1 Find the coordinates of each point. F(1, 2), G(5, 5), J(–4, 0), K(–1, –3)

15. Holt McDougal Geometry 1-6 Midpoint and Distance in the Coordinate Plane Example 5 Step 2 Use the Distance Formula.

16. Holt McDougal Geometry 1-6 Midpoint and Distance in the Coordinate Plane You can also use the Pythagorean Theorem to find the distance between two points in a coordinate plane.** You will learn more about the Pythagorean Theorem in Chapter 5.**

17. Holt McDougal Geometry 1-6 Midpoint and Distance in the Coordinate Plane In a right triangle, the two sides that form the right angle are the legs. The side across from the right angle that stretches from one leg to the other is the hypotenuse.

18. Holt McDougal Geometry 1-6 Midpoint and Distance in the Coordinate Plane In the diagram, a and b are the lengths of the shorter sides, or legs, of the right triangle. The longest side is called the hypotenuse and has length c. a

19. Holt McDougal Geometry 1-6 Midpoint and Distance in the Coordinate Plane Example 4: Finding Distances in the Coordinate Plane Use the Distance Formula and the Pythagorean Theorem to find the distance. A (-2,3) B(2,-2) 5 4

20. Holt McDougal Geometry 1-6 Midpoint and Distance in the Coordinate Plane Example 4 Continued Method 1 Use the Distance Formula. Substitute the values for the coordinates into the Distance Formula.

21. Holt McDougal Geometry 1-6 Midpoint and Distance in the Coordinate Plane Method 2 Use the Pythagorean Theorem. Example 4 Continued a = 5 and b = 4. c 2 = a 2 + b 2 c 2 = 5 2 + 4 2 c 2 = 25 + 16 c 2 = 41 c =

22. Holt McDougal Geometry 1-6 Midpoint and Distance in the Coordinate Plane Check It Out! Example 4a Use the Distance Formula and the Pythagorean Theorem to find the distance, to the nearest tenth, from R to S. R(3, 2) and S(–3, –1) Method 1 Use the Distance Formula. Substitute the values for the coordinates of R and S into the Distance Formula.

23. Holt McDougal Geometry 1-6 Midpoint and Distance in the Coordinate Plane Check It Out! Example 4a Continued Use the Distance Formula and the Pythagorean Theorem to find the distance, to the nearest tenth, from R to S. R(3, 2) and S(–3, –1)