Proving a trigonometric identity

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Discussion Overview

The discussion revolves around the verification of a trigonometric identity presented by a participant. The scope includes mathematical reasoning and attempts to prove the identity through various methods.

Discussion Character

  • Debate/contested, Mathematical reasoning

Main Points Raised

  • One participant seeks assistance in proving the identity: $$\frac{\cot^2(x)-\cot(x)+1}{1-2\tan(x)+\tan^2(x)}=\frac{1+\cot^2(x)}{1+\tan^2(x)}$$.
  • Another participant questions the validity of the identity, suggesting that the provided equation is not true.
  • A participant reiterates the original identity as stated in the thread and asserts that it is not an identity.
  • One participant defines a trigonometric identity as an equation that holds true for all legitimate values of the variables involved, noting that the given equation is only true for specific values of $$x$$.
  • Another participant mentions using Wolfram Alpha (W|A) to check the validity of trigonometric identities, indicating that many given identities may not actually hold true.

Areas of Agreement / Disagreement

Participants express disagreement regarding the validity of the proposed trigonometric identity, with some asserting it is not an identity and others seeking clarification on its legitimacy.

Contextual Notes

There is uncertainty regarding the conditions under which the proposed identity may hold true, as well as the definitions and interpretations of what constitutes a trigonometric identity.

egillesp
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Hi,

I need help proving the following trig identity:

$$\frac{\cot^2(x)-\cot(x)+1}{1-2\tan(x)+\tan^2(x)}=\frac{1+\cot^2(x)}{1+\tan^2(x)}$$

Me and my friend have spent several hours determined to figure this out, starting from the left hand side, the right hand side, and doing both together, but nothing seems to work.
For example, I tried to factor the left hand side, $$\frac{(\cot(x)-1)^2}{(\tan(x)-1)^2}$$, but it didn't get me anywhere.

Help would be greatly appreciated
 
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I tried fixing your $\LaTeX$, and the resulting identity is not true...can you clarify what the actual given identity should be?
 
The actual given identity is what I posted in the title and first thing in the thread
 
egillesp said:
The actual given identity is what I posted in the title and first thing in the thread

The equation given in your first post is not an identity. :D
 
okay, so what do you mean by a trig identity?
 
egillesp said:
okay, so what do you mean by a trig identity?

An identity is an equation that is true for all legitimate values of any variables in the equation.

The equation you posted is only true for:

$$x=\frac{\pi}{2}(2k\pm1)$$ where $$k\in\mathbb{Z}$$
 
okay thank you
 
egillesp said:
okay thank you

One of the first things I do when someone posts a trigonometric identity is to use W|A to check to see if it is in fact an identity, because often enough the given identity is in fact not true, and this saves a lot of time and hair pulling. :D

Here is where I checked:

>>click here<<
 

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