2Objectives: Find the midpoint of a segment. Find the distance between two points using the distance formula and Pythagorean’s Theorem.
3Midpoint of a SegmentThe midpoint of a segment is the point halfway between the endpoints of the segment. If X is the midpoint of AB, then AX XB.To find the midpoint of a segment on a number line find ½ of the sum of the coordinates of the two endpoints.a + b2
4Segment BisectorA segment bisector is a point, ray, line, line segment, or plane that intersects the segment at its midpoint.
5Example 1:The coordinates on a number line of J and K are –12 and 16, respectively. Find the coordinate of the midpoint of .The coordinates of J and K are –12 and 16.Let M be the midpoint of .Simplify.Answer: 2
6Example 2:Multiple-Choice Test Item What is the measure of if Q is the midpoint of ?A B 4 C D 9
7Example 2: Read the Test Item You know that Q is the midpoint of , and the figure gives algebraic measures for and . You are asked to find the measure of .Solve the Test ItemBecause Q is the midpoint, you know that .Use this equation and the algebraic measures to find avalue for x.
8Example 2: Definition of midpoint Distributive Property Subtract 1 from each side.Add 3x to each side.Divide each side by 10.
9Example 2: Now substitute for x in the expression for PR. Original measureSimplify.Answer: D
10Your Turn:Multiple-Choice Test Item What is the measure of if B is the midpoint of ?A 1 B 3 C 5 D 10Answer: D
11Midpoint of a Segment M ( x1 + x2 , y1 + y2 ) 2 2 If the segment is on a coordinate plane, we must use the midpoint formula for coordinate planes which states given a segment with endpoints (x1, y1) and (x2 , y2) the midpoint is…M ( x1 + x2 , y1 + y2 )
12Example 3:Find the coordinates of M, the midpoint of , for G(8, –6) and H(–14, 12).Let G be and H be .-Answer: (–3, 3)
13Your Turn:a. The coordinates on a number line of Y and O are 7 and –15, respectively. Find the coordinate of the midpoint of .b. Find the coordinates of the midpoint of for X(–2, 3) and Y(–8, –9).Answer: –4Answer: (–5, –3)
14More About MidpointsYou can also find the coordinates of an endpoint of a segment if you know the coordinates of the other endpoint and the midpoint.
15Example 4:Find the coordinates of D if E(–6, 4) is the midpoint of and F has coordinates (–5, –3).Let F be in the Midpoint Formula.Write two equations to find the coordinates of D.
16Example 4: Solve each equation. Multiply each side by 2. Add 5 to each side.Multiply each side by 2.Add 3 to each side.Answer: The coordinates of D are (–7, 11).
17Your Turn:Find the coordinates of R if N(8, –3) is the midpoint of and S has coordinates (–1, 5).Answer: (17, –11)
18Distance Between Two Points In previous sections we learned that whenever you connect two points you create a segment.We also learned every segment has a measure.The distance between two points, or the measure of a segment, is determined by the number of units between the two points.
19Distance Formula on a Number Line If a segment is on a number line, we simply find its length by using the Distance Formula which states the distance between two points is the absolute value of the difference of the values of the two points.| A – B | = | B – A | = Distance
20Example 5: Use the number line to find QR. The coordinates of Q and R are –6 and –3.Distance FormulaSimplify.Answer: 3
21Your Turn:Use the number line to find AX.Answer: 8
22Distance Formula on a Coordinate Plane Segments may also be drawn on coordinate planes. To find the distance between two points on a coordinate plane with coordinates (x1, y1) and (x2, y2) we can use this formula:
23Distance Formula on a Coordinate Plane … or we can use the Pythagorean Theorem.The Pythagorean Theorem simply states that the square of the hypotenuse equals the sum of the squares of the two legs.a2 + b2 = c2
24Example 6: Find the distance between E(–4, 1) and F(3, –1). Pythagorean Theorem MethodUse the gridlines to form a triangle so you can use the Pythagorean Theorem.
25Example 6: Pythagorean Theorem Simplify. Take the square root of each side.
26Example 6: Distance Formula Method Distance Formula Simplify. Answer: The distance from E to F is units. You can use a calculator to find that is approximately 7.28.
27Your Turn:Find the distance between A(–3, 4) and M(1, 2).Answer: