sum and diff of sine o5 o5 o5

8/12/2019 Sum and Diff of Sine o5 o5 o5

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Sum and Difference Formulas of Sine

DATE: January 14, 2014

I. OBJECTIVES

At the end of the lesson, the students must be able to:

1. State the sum and difference formulas of sine;

2. Express a measure as a sum or difference of two angles; and

3. Determine the sine of an angle using the sum and difference formula.

II. SUBJECT MATTER

A. Topic: Sum and Difference Formulas of Sine

B. Reference: Advanced Algebra, Trigonometry and Statistics Textbook for

Fourth Year, pp. 203-205

C. Materials: Chalkboard, visual aids, activity tools

III. PROCEDURE

A. Routinary Activities

1. Prayer

2. Greeting the class

3. Setting the classroom atmosphere

4. Checking of the attendance

B. Review/Motivation

The QCR GameMECHANICS:

1. The game begins with the facilitator giving the ball to the chosen student.

2. The teacher will ask the student to choose a number ranging from 5-10. Then,

the student will pass the ball to her/his left or right.


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3. The student will count according to her/his given number and when the count

stopped to that student, she/he will be the one who will go in front and pick 1

question in the container that contains set of questions. She/he will read the

question and will be given 1 minute to answer the question.

4. If the student will be able to answer the question within 1 minute, she/he canpick her/his reward from the container that contains rewards but if she/he wont

be able to answer the question, she/he must pick her/his consequence from the

container, contains set of consequences and the student must do what is stated on

the consequence he/she picked.

5. After that, the game continues, same procedure, until all the set of questions has

been picked.

C. Lesson Proper

ReviewState the Sum and Difference Formula of Cosine

( ) ( )

How to evaluate the function cos -120 1. Think of two special angles that when you add or subtract, you will

get 120.

2. Let the second angle.3. Use the given formula of sum and difference of cosine.

4. Find the coordinates of the angle then evaluate the function.

What is the pattern in finding the sum and difference of cosine?

cos cos sin sin

Discussion(The teacher will discuss first the objectives.)

( )

The sine of the sum of two angles is equal to the product of the

sine of the first and the cosine of the second plus the product of the cosine

of the first and the sine of the second. In symbol,


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EXAMPLE:

Express sin 120 90

Let =60 ( )

(

)

= +

= +

=

sin 120 = Boardwork

Express sin 15 45

Let =45 ( )

( )

and =

( )

The sine of the difference of two angles is equal to the product of

the sine of the first and the cosine of the second minus the product of the

cosine of the first and the sine of the second. In symbol,


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=

sin 15 = Generalization

() ()

( ) ( )

STEPS:1. Think of two special angles that when you add or subtract, the result

will be the given angle.

2. Let be the first angle and the second angle.3. Use the sum and difference formulas of sine.4. Find the coordinates of the angles then evaluate the function.

IV. EVALUATION

(The teacher divided the class into 4 groups. They will answer the question

individually but their group must derived at only one answer.)

Express sin75as sum of two angles; sin 90as difference of two angles.Find its exact value.sin 75=> and sin (45 )

=

=

sin 75 =

sin 90 and sin (30) sin

= (-)


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= ( )

=+

=

sin 90

V. ASSIGNMENT

Since tomorrow is your 3rd Periodical Exam, there will be no assignment.Recall the topics from 3

rdGrading Period. Study hard and GodBless.

VI. REMARKS

sum and diff of sine o5 o5 o5

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