Comprehension

Consider the following for the three (03) items that follow:
Let p = tan 2α   - tanα and q = cotα - cot 2α

What is tan2α equal to?

This question was previously asked in
NDA-I (Mathematics) Official Paper (Held On: 13 Apr, 2025)
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  1. (pq)/(p+q)
  2. (p+2q)/p
  3. p/(p+2q)
  4. p/(2p+q)

Answer (Detailed Solution Below)

Option 3 : p/(p+2q)
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Detailed Solution

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Calculation: 

We are given:

\( p = \tan(2\alpha) - \tan(\alpha) \)

\( q = \cot(\alpha) - \cot(2\alpha) \)

We need to find \(\tan^2(\alpha) \) in terms of p  and q .

We start by simplifying the expression \(\frac{p}{p + 2q} \)

\( \frac{p}{p + 2q} = \frac{1}{1 + \frac{2q}{p}} \)

This simplifies further as:

\( \frac{1}{1 + \frac{2}{\tan(\alpha) \cdot \tan(2\alpha)}} \)

Now, simplify the fraction inside the denominator:

\( = \frac{1}{1 + \frac{2}{\tan(\alpha) \cdot \tan(2\alpha)}} = \frac{1}{1 + \frac{1}{2} \cdot \tan(\alpha) \cdot \tan(2\alpha)} \)

Now, expand both terms using trigonometric identities:

\( = \frac{\sin(\alpha) \cdot \sin(2\alpha)}{\sin(\alpha) \cdot \cos(\alpha) + \cos(\alpha) \cdot \cos(2\alpha)} \)

Simplifying this expression gives:

\( = \tan^2(\alpha) \)

∴ The correct answer is Option (c):

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