Answer :

To determine whether [tex]\(\frac{1 - \sin(2x)}{1 + \sin(2x)} = \tan^2\left(\frac{\pi}{4} - x\right)\)[/tex], let's analyze both expressions and simplify them to see if they are equivalent.

### Simplifying [tex]\(\frac{1 - \sin(2x)}{1 + \sin(2x)}\)[/tex]:

Given:
[tex]\[ \frac{1 - \sin(2x)}{1 + \sin(2x)} \][/tex]

### Simplifying [tex]\(\tan^2\left(\frac{\pi}{4} - x\right)\)[/tex]:

1. Recall that [tex]\(\tan\left(\frac{\pi}{4} - x\right) = \frac{\tan\left(\frac{\pi}{4}\right) - \tan(x)}{1 + \tan\left(\frac{\pi}{4}\right)\tan(x)}\)[/tex].

2. Since [tex]\(\tan\left(\frac{\pi}{4}\right) = 1\)[/tex], substitute [tex]\(\tan\left(\frac{\pi}{4}\right) \)[/tex]:

[tex]\[ \tan\left(\frac{\pi}{4} - x\right) = \frac{1 - \tan(x)}{1 + \tan(x)} \][/tex]

3. Now square both sides:

[tex]\[ \tan^2\left(\frac{\pi}{4} - x\right) = \left(\frac{1 - \tan(x)}{1 + \tan(x)}\right)^2 \][/tex]

### Checking Equivalent of Both Simplified Expressions

1. Our goal is to see if:

[tex]\[ \frac{1 - \sin(2x)}{1 + \sin(2x)} = \left(\frac{1 - \tan(x)}{1 + \tan(x)}\right)^2 \][/tex]

Given these steps and simplifications, compare them:
- The first simplified expression: [tex]\(\frac{1 - \sin(2x)}{1 + \sin(2x)} \)[/tex]
- The second simplified expression: [tex]\(\cot^2(x + \frac{\pi}{4})\)[/tex]

### Conclusion
Upon analyzing both simplified expressions and their computations showed no equality. Therefore, they are not equivalent:

[tex]\[ \frac{1 - \sin(2x)}{1 + \sin(2x)} \neq \tan^2\left(\frac{\pi}{4} - x\right) \][/tex]

Thus, the initial equation does not hold true:
[tex]\[ \frac{1 - \sin(2x)}{1 + \sin(2x)} \neq \tan^2\left(\frac{\pi}{4} - x\right) \][/tex]

So, the proposition is false.