Angle BisectorThursday, June 27, 2013I. Objectives

At the end of the lesson, at least 75 % of the students are expected to have 75 % mastery and should be able to:

a. Define angle bisectorb. Identify the bisector of an anglec. Illustrate the bisector of an angle

II. Subject MatterA. Angle BisectorB. References

MSA GEOMETRYMathematics III

III. Teaching Learning SequenceCritical Question: If ray AD is in between of angle BAC, and the 2 angles formed are congruent, what is true about this ray AD?

Activity 1Ask the students to bring out the materials needed for this activity and follow the procedure to be stated by the teacher. Procedure

1. On a piece of paper, draw an angle of 60 degrees. Name it as angle BAC2. Fold the paper such that the rays coincide with each other.3. Make a crease.4. Unfold the paper. Trace the crease by drawing ray AD.5. Measure the angles formed by the crease.

Guide Questions

1. What is the sum of angles DAB and DAC?2. How do you compare the 2 angles in number 2?3. What do you call to ray AD that divides these angles into two congruent parts?

Activity 2

Complete the following statement.1. Two angles are congruent if they have the same ___________.2. Ray OS bisects angle POR, angle POS is _______ angle SOR.3. The bisector of angle forms 2 _________ angles.4. The bisector of an obtuse angle forms 2 _________ angles.

Application of angle bisectorPractice Exercises

In the figure below, ray OM bisects angle NOK and OL bisects angle NOM. Given the following conditions, find the value of x and the indicated angle.

1. Angle MON= 2x+13 angle MOK= 732. Angle MOK= 3x+10, angle NOK= 1603. Angle NOL= 31-x, angle LOM= 614. Angle NOM= 85, angle NOL= 2x-5

IV. Generalization

An angle bisector is a ray that divides an angle into two congruent anglesV. Evaluation

1. Ray BD bisects angle ABC. Find angle ABC, angle CBP, and angle DBAa.

Angle ABD= 2x-3 Angle DBC=x+12

Angle ABD= 2x2 Angle ABC=64

VI. Assignment

1. Reviewl all angle pairs