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Equidistant. A point is equidistant from two figures if the point is the same distance from each figure. Examples: midpoints and parallel lines. 5.2-5.4: Special Segments. Objectives: To use and define perpendicular bisectors, angle bisectors, medians, and altitudes
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Equidistant A point is equidistantfrom two figures if the point is the same distance from each figure. Examples: midpoints and parallel lines
5.2-5.4: Special Segments Objectives: • To use and define perpendicular bisectors, angle bisectors, medians, and altitudes • To discover, use, and prove various theorems about perpendicular bisectors and angle bisectors
Perpendicular Bisector Theorem In a plane, if a point is on the perpendicular bisector of a segment, then it is equidistant from the endpoints of the segment.
Converse of Perpendicular Bisector Theorem In a plane, if a point is equidistant from the endpoints of a segment, then it is on the perpendicular bisector of the segment.
Example 1 Plan a proof for the Perpendicular Bisector Theorem. 1. AB CP Given 2. AP = PB Def. of Bisector 3. <CPB & Def. of Perp. <CPA R rt. <s 4. <CPB=<CPA All rt. <s R = CP = CP Reflexive CAP = CBP SAS CA = CB CPCTC ~ ~ ~ ~ ~ ~
Example 2 BD is the perpendicular bisector of AC. Find AD. X=7 AD=35
Example 3 Find the values of x and y. x=12 y=8
Angle Bisector An angle bisector is a ray that divides an angle into two congruent angles.
Angle Bisector Theorem If a point is on the bisector of an angle, then it is equidistant from the two sides of the angle.
Example 4 A soccer goalie’s position relative to the ball and goalposts forms congruent angles, as shown. Will the goalie have to move farther to block a shot toward the right goal post or the left one? Answer in your notebook
Example 5 Find the value of x. x=5
Example 6 Find the measure of <GFJ. It’s not the Angle Bisector Theorem that could help us answer this question. It’s the converse. If it’s true.
Converse of the Angle Bisector Theorem If a point is in the interior of an angle and is equidistant from the sides of the angle, then it lies on the bisector of the angle.
Example 7 For what value of x does P lie on the bisector of <A? x=4
Special Triangle Segments Both perpendicular bisectors and angle bisectors are often associated with triangles, as shown below. Triangles have two other special segments. Perpendicular Bisector Angle Bisector
Median A medianof a triangle is a segment from a vertex to the midpoint of the opposite side of the triangle.
Altitude The length of the altitude is the height of the triangle. An altitudeof a triangle is a perpendicular segment from a vertex to the opposite side or to the line that contains that side.
Example 8 Is it possible for any of the aforementioned special segments to be identical? In other words, is there a triangle for which a median, an angle bisector, and an altitude are all the same?