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(C) [tex]\frac{\cos A - \sin A}{\cos A + \sin A} = \sec 2A - \tan 2A[/tex]

Sagot :

Let's solve the equation \(\frac{\cos A - \sin A}{\cos A + \sin A} = \sec(2A) - \tan(2A)\) step by step.

First, consider the left-hand side of the equation:

[tex]\[ \text{Left-hand side: } \frac{\cos A - \sin A}{\cos A + \sin A} \][/tex]

Next, let's consider the right-hand side of the equation:

[tex]\[ \text{Right-hand side: } \sec(2A) - \tan(2A) \][/tex]

Now let's break it down.

### Simplifying the Left-Hand Side
The left-hand side is already in a simplified form involving trigonometric functions:

[tex]\[ \frac{\cos A - \sin A}{\cos A + \sin A} \][/tex]

### Simplifying the Right-Hand Side
Evaluate the right-hand side using known trigonometric identities:

[tex]\[ \sec(2A) = \frac{1}{\cos(2A)}, \quad \tan(2A) = \frac{\sin(2A)}{\cos(2A)} \][/tex]

Thus, the right-hand side can be written as:

[tex]\[ \sec(2A) - \tan(2A) = \frac{1}{\cos(2A)} - \frac{\sin(2A)}{\cos(2A)} = \frac{1 - \sin(2A)}{\cos(2A)} \][/tex]

### Comparing Both Sides
To check the equality, let's compare:

[tex]\[ \frac{\cos A - \sin A}{\cos A + \sin A} \quad \text{and} \quad \frac{1 - \sin(2A)}{\cos(2A)} \][/tex]

Upon simplifying expressions and calculations, we find that:

[tex]\[ \frac{\cos A - \sin A}{\cos A + \sin A} = \frac{1}{\tan(A + \frac{\pi}{4})} \][/tex]

Whereas:

[tex]\[ \sec(2A) - \tan(2A) = -\tan(2A) + \sec(2A) \][/tex]

### Conclusion
Upon simplification, it is evident that the two expressions:

[tex]\[ \frac{\cos A - \sin A}{\cos A + \sin A} \quad \text{and} \quad \sec(2A) - \tan(2A) \][/tex]

do not simplify to the same value. Hence, the given equation:

[tex]\[ \frac{\cos A - \sin A}{\cos A + \sin A} = \sec(2A) - \tan(2A) \][/tex]

is not true.