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Question

For the following two (02) items: 

Let $\frac{1+\sin\theta}{\cos\theta} = p + \sqrt{p^2+1}$.

What is \(\tan\theta\) equal to?

This question was previously asked in
CDS 2 2025 Maths Question Paper (14-Sep-2025)
The correct answer is
\(p\)

Trigonometric Solution: Finding \(\tan\theta\)

This problem involves simplifying a trigonometric expression and using fundamental identities to find the value of \(\tan\theta\) in terms of the variable \(p\). We are given the equation:

\(\frac{1+\sin\theta}{\cos\theta} = p + \sqrt{p^2+1}\)

Step 1: Simplify the Left-Hand Side Expression

We can rewrite the left-hand side (LHS) of the equation using basic trigonometric definitions:

  • Recall that \(\sec\theta = \frac{1}{\cos\theta}\) and \(\tan\theta = \frac{\sin\theta}{\cos\theta}\).

Splitting the fraction:

\(\frac{1+\sin\theta}{\cos\theta} = \frac{1}{\cos\theta} + \frac{\sin\theta}{\cos\theta}\)

Substituting the identities:

\(\sec\theta + \tan\theta\)

So, the given equation can be expressed as:

\(\sec\theta + \tan\theta = p + \sqrt{p^2+1}\)

Step 2: Utilize the Pythagorean Identity

We know the fundamental Pythagorean identity involving secant and tangent:

\(\sec^2\theta - \tan^2\theta = 1\)

This identity can be factored as a difference of squares:

\((\sec\theta - \tan\theta)(\sec\theta + \tan\theta) = 1\)

From this, we can express \((\sec\theta - \tan\theta)\) in terms of \((\sec\theta + \tan\theta)\):

\(\sec\theta - \tan\theta = \frac{1}{\sec\theta + \tan\theta}\)

Step 3: Substitute and Solve for \((\sec\theta - \tan\theta)\)

Using the result from Step 1, substitute the value of \((\sec\theta + \tan\theta)\):

\(\sec\theta - \tan\theta = \frac{1}{p + \sqrt{p^2+1}}\)

To simplify this expression, we rationalize the denominator by multiplying the numerator and denominator by the conjugate (\(p - \sqrt{p^2+1}\)):

\(\sec\theta - \tan\theta = \frac{1}{p + \sqrt{p^2+1}} \times \frac{p - \sqrt{p^2+1}}{p - \sqrt{p^2+1}}\)

\(\sec\theta - \tan\theta = \frac{p - \sqrt{p^2+1}}{p^2 - (\sqrt{p^2+1})^2}\)

\(\sec\theta - \tan\theta = \frac{p - \sqrt{p^2+1}}{p^2 - (p^2+1)}\)

\(\sec\theta - \tan\theta = \frac{p - \sqrt{p^2+1}}{-1}\)

\(\sec\theta - \tan\theta = \sqrt{p^2+1} - p\)

Step 4: Solve the System of Equations for \(\tan\theta\)

Now we have a system of two linear equations with \(\sec\theta\) and \(\tan\theta\):

  1. \(\sec\theta + \tan\theta = p + \sqrt{p^2+1}\)
  2. \(\sec\theta - \tan\theta = \sqrt{p^2+1} - p\)

To find \(\tan\theta\), subtract the second equation from the first equation:

\((\sec\theta + \tan\theta) - (\sec\theta - \tan\theta) = (p + \sqrt{p^2+1}) - (\sqrt{p^2+1} - p)\)

\(\sec\theta + \tan\theta - \sec\theta + \tan\theta = p + \sqrt{p^2+1} - \sqrt{p^2+1} + p\)

Combine like terms:

\(2\tan\theta = 2p\)

Divide by 2:

\(\tan\theta = p\)

Conclusion

By simplifying the given trigonometric expression and applying the Pythagorean identity, we found that \(\tan\theta\) is equal to \(p\).

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Similar Questions

  1. If \(\sqrt{2+\sqrt{2+\sqrt{2+\sqrt{2+...}}}} = \text{cosec}\theta\), then what is \(\sin\theta\) equal to?

  2. If \(2 \tan\theta = \sec^2\theta-2\), where \(0 < \theta < \pi /2\), then what is \(\cot\theta\) equal to?
  3. What is \(\frac{\tan^2 \alpha}{\tan^2 \beta}\) equal to?
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  8. Consider the following statements :
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Important Questions from Trigonometry

  1. (secθ + tanθ)/(secθ - tanθ)  is equal to:

  2. If tan 45°, cot θ then the value of θ, in radians is

  3. ABC is a triangle If sin (A+B)/2 = √3/2, then the value of sin C/2 is

  4. The angles of elevation of the top of a temple, from the foot and the top of a building 30 m high, are 60° and 30° respectively. Then height of the temple is

  5. The value of sin θ and cos θ when the angle θ is 0 ≤ θ ≤ 90°, is ______

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