How? Which Trig Identityis that?

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Homework Help Overview

The discussion revolves around trigonometric identities, specifically focusing on the manipulation and application of these identities in a given equation. Participants are examining the correctness of a proposed identity and its relevance to a problem in electrical engineering.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants are questioning the validity of a proposed trigonometric identity and discussing related identities. There is an exploration of how these identities can be applied to a specific equation, with some participants suggesting corrections and clarifications.

Discussion Status

The discussion is active, with participants providing feedback on the original post's equation and suggesting relevant trigonometric identities. There is a recognition of potential errors in the initial setup, and some participants are offering alternative identities for consideration.

Contextual Notes

There is mention of a specific electrical engineering context, referencing a textbook, which may influence the interpretation of the identities being discussed. Participants are also reflecting on the accuracy of the original equation presented in the thread.

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How?? Which Trig Identityis that?

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The Attempt at a Solution


sin^2 = 1- cos^2 ??
 
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That looks wrong. It is close to the identity.

$$2\sin^2(x-\pi/4)=1-\sin(2x)$$
 
Yes. one of the relevant equation is sin2θ=1-cos2θ.
The other one is cos(2θ)=cos2θ-sin2θ. From these, you get the identity

sin2θ=.5(1-cos(2θ)). Use it.ehild
 
ehild said:
Yes. one of the relevant equation is sin2θ=1-cos2θ.
The other one is cos(2θ)=cos2θ-sin2θ. From these, you get the identity

sin2θ=.5(1-cos(2θ)). Use it.


ehild

but there is no sin..
 
k31453 said:
but there is no sin..

The equation you wrote in the first post is wrong. Correctly, it should be:

2000sin2(500πt)=1000(1-cos(1000πt)).

ehild
 
ehild said:
The equation you wrote in the first post is wrong. Correctly, it should be:

2000sin2(500πt)=1000(1-cos(1000πt)).

ehild

Awaks.. IT is solution of the Electrical Engineer : priniciples and application Hambley book.

And they made it wrong. I asked the question though i was wrong.
 

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