Book demonstration about trigonometric relations

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Homework Help Overview

The discussion revolves around a trigonometric identity presented in a book, specifically questioning the author's statements regarding the relationship between certain trigonometric functions and their absolute values.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants are exploring the validity of the author's claims about trigonometric identities, particularly focusing on the use of absolute values and the specific functions involved, such as sine and cosine. There is confusion regarding the correctness of the identity and the implications of the absolute value in the context of the problem.

Discussion Status

The discussion is active, with participants questioning the reasoning behind the author's statements and seeking clarification on the relationships between the trigonometric functions. Some guidance has been offered regarding the nature of multiplication and its commutative property, but there remains a lack of consensus on the interpretation of the identity in question.

Contextual Notes

Participants express confusion over the specific trigonometric functions involved and the implications of using absolute values in the context of the problem. There is an indication that the original problem may have constraints or specific requirements that are not fully articulated in the discussion.

Bunny-chan
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Homework Statement


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[/B]

In the equation between (3) and (2), why does the author says that
4853327b00864221b28222f8ec109261.png
? Isn't the trigonometric identity actually
b1d600bf2773406fb9443fa8e18b6fac.png
?

2. Homework Equations

The Attempt at a Solution

 

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You are right, but that doesn't mean that what they say is wrong. In fact it proves that their statements are correct. They want to prove something about the absolute value, so they took the absolute value of both sides.
 
FactChecker said:
You are right, but that doesn't mean that what they say is wrong. In fact it proves that their statements are correct. They want to prove something about the absolute value, so they took the absolute value of both sides.
Sorry, I don't understand what you mean. How does it prove his statement is correct?

I wasn't wondering about the absolute values, I was confused about the fact that it should be two times the cosine, not the sine.
 
Bunny-chan said:
Sorry, I don't understand what you mean. How does it prove his statement is correct?

I wasn't wondering about the absolute values, I was confused about the fact that it should be two times the cosine, not the sine.
It's the same thing. Multiplication is commutative. They just swapped the order of the multiplication.
 
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