All Exams Test series for 1 year @ ₹349 only
Question

Let 12 $ (\tan \theta + \cot \theta) = 25 $, where $ 45^\circ < \theta < 90^\circ $

What is a value of (sinθ - cosθ) ?

This question was previously asked in
CDS 2 2026 Maths Question Paper (13-Sep-2026)
The correct answer is
\(\frac{1}{5}\)

Simplify tanθ and cotθ Equation

Given the equation \(12 (\tan \theta + \cot \theta) = 25\) and the range \(45^\circ < \theta < 90^\circ\). We need to find the value of \((\sin \theta - \cos \theta)\).

Rewrite \(\tan \theta\) and \(\cot \theta\) using \(\sin \theta\) and \(\cos \theta\):

  • \(\tan \theta = \frac{\sin \theta}{\cos \theta}\)
  • \(\cot \theta = \frac{\cos \theta}{\sin \theta}\)

Substitute into the equation:

\(12 \left( \frac{\sin \theta}{\cos \theta} + \frac{\cos \theta}{\sin \theta} \right) = 25\)

Find a common denominator:

\(12 \left( \frac{\sin^2 \theta + \cos^2 \theta}{\sin \theta \cos \theta} \right) = 25\)

Apply the identity \(\sin^2 \theta + \cos^2 \theta = 1\):

\(12 \left( \frac{1}{\sin \theta \cos \theta} \right) = 25\)

\(\frac{12}{\sin \theta \cos \theta} = 25\)

Solve for the product \(\sin \theta \cos \theta\):

\(\sin \theta \cos \theta = \frac{12}{25}\)

Calculate (sinθ - cosθ)² Value

Consider the square of the target expression \((\sin \theta - \cos \theta)\):

\((\sin \theta - \cos \theta)^2 = \sin^2 \theta - 2 \sin \theta \cos \theta + \cos^2 \theta\)

Group terms and use the identity \(\sin^2 \theta + \cos^2 \theta = 1\):

\((\sin \theta - \cos \theta)^2 = (\sin^2 \theta + \cos^2 \theta) - 2 \sin \theta \cos \theta\)

\((\sin \theta - \cos \theta)^2 = 1 - 2 \sin \theta \cos \theta\)

Substitute the value of \(\sin \theta \cos \theta\):

\((\sin \theta - \cos \theta)^2 = 1 - 2 \left( \frac{12}{25} \right) = 1 - \frac{24}{25}\)

\((\sin \theta - \cos \theta)^2 = \frac{25 - 24}{25} = \frac{1}{25}\)

Determine (sinθ - cosθ) Sign

Take the square root of both sides:

\(\sin \theta - \cos \theta = \pm \sqrt{\frac{1}{25}} = \pm \frac{1}{5}\)

Analyze the sign based on the given range \(45^\circ < \theta < 90^\circ\):

  • In this range, \(\theta\) is in the first quadrant.
  • \(\sin \theta\) and \(\cos \theta\) are both positive.
  • For angles greater than \(45^\circ\) (up to \(90^\circ\)), \(\sin \theta > \cos \theta\).

Therefore, \((\sin \theta - \cos \theta)\) must be positive.

Final (sinθ - cosθ) Result

Select the positive value:

\(\sin \theta - \cos \theta = \frac{1}{5}\)

Was this answer helpful?

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?
  4. If \(\alpha\) and \(\beta\) are complementary angles, then which one of the following is correct?
  5. What is \(\sec\theta\) equal to?
  6. What is \(\tan\theta\) equal to?
  7. What is the relation between \(p\) and \(q\)?
  8. What is $\tan\theta + \cot\theta$ equal to?
  9. Consider the following statements :
    1. In a triangle ABC, if \(\sin A + \sin B + \sin C = \frac{3\sqrt{3}}{2}\), then the triangle can be equilateral.
    2. In a triangle ABC, if \(\cos A + \cos B + \cos C = \frac{3}{2}\), then the triangle can be equilateral.
    Which of the statements given above is/are correct?
  10. What is \((1 + \tan\alpha \tan\beta)^2 + (\tan\alpha - \tan\beta)^2\) equal to ?


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 ______

Need Expert Advice?
Test Series
CDS img
Defence
UPSC CDS 2026 Mock Test Series
559 Tests 4 Tests Free
1783 Attempts
4.3(193)
English, Hindi
More Questions from CDS

Start Your Preparation with Prepp Mobile App

Download the app from Google Play & App Store
Download the app from Google Play & App Store
Prepp Mobile App