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If cosec θ - sin θ = p 3and sec θ - cos θ = q 3, then what is the value of tan θ ?

This question was previously asked in
CDS I 2020 Elementary Mathematics Previous Year Paper (02-Feb-2020)
The correct answer is \(\dfrac{q}{p}\)

Understanding the Problem: Finding tan θ

We are given two trigonometric equations involving \(\operatorname{cosec} \theta\)< /span>, \(\sin \theta\)< /span>, \(\sec \theta\)< /span>, and \(\cos \theta\)< /span>, and we need to find the value of \(\tan \theta\)< /span> in terms of \(p\)< /span> and \(q\)< /span>. The given equations are:

  • \(\operatorname{cosec} \theta - \sin \theta = p^3\)< /span>
  • \(\sec \theta - \cos \theta = q^3\)< /span>

Our goal is to manipulate these equations to find an expression for \(\tan \theta\)< /span>, which is defined as \(\tan \theta = \frac{\sin \theta}{\cos \theta}\)< /span>.

Simplifying the Equation for p

Let's start with the first equation:

\(\operatorname{cosec} \theta - \sin \theta = p^3\)< /span>

We know that \(\operatorname{cosec} \theta = \frac{1}{\sin \theta}\)< /span>. Substituting this into the equation:

\(\frac{1}{\sin \theta} - \sin \theta = p^3\)< /span>

To combine the terms on the left side, we find a common denominator:

\(\frac{1 - \sin^2 \theta}{\sin \theta} = p^3\)< /span>

Using the fundamental Pythagorean identity \(\sin^2 \theta + \cos^2 \theta = 1\)< /span>, we can replace \(1 - \sin^2 \theta\)< /span> with \(\cos^2 \theta\)< /span>:

\(\frac{\cos^2 \theta}{\sin \theta} = p^3\)< /span> (Equation 1')

Simplifying the Equation for q

Now, let's work with the second equation:

\(\sec \theta - \cos \theta = q^3\)< /span>

We know that \(\sec \theta = \frac{1}{\cos \theta}\)< /span>. Substituting this:

\(\frac{1}{\cos \theta} - \cos \theta = q^3\)< /span>

Finding a common denominator:

\(\frac{1 - \cos^2 \theta}{\cos \theta} = q^3\)< /span>

Again, using the identity \(\sin^2 \theta + \cos^2 \theta = 1\)< /span>, we replace \(1 - \cos^2 \theta\)< /span> with \(\sin^2 \theta\)< /span>:

\(\frac{\sin^2 \theta}{\cos \theta} = q^3\)< /span> (Equation 2')

Deriving the Value of tan θ

We now have two simplified equations:

  • Equation 1': \(\frac{\cos^2 \theta}{\sin \theta} = p^3\)< /span>
  • Equation 2': \(\frac{\sin^2 \theta}{\cos \theta} = q^3\)< /span>

We want to find \(\tan \theta\)< /span>, which is \(\frac{\sin \theta}{\cos \theta}\)< /span>. Let's divide Equation 2' by Equation 1' to see if we can get \(\tan \theta\)< /span>:

\(\frac{\left( \frac{\sin^2 \theta}{\cos \theta} \right)}{\left( \frac{\cos^2 \theta}{\sin \theta} \right)} = \frac{q^3}{p^3}\)< /span>

Simplify the left side by multiplying by the reciprocal of the denominator:

\(\frac{\sin^2 \theta}{\cos \theta} \times \frac{\sin \theta}{\cos^2 \theta} = \frac{q^3}{p^3}\)< /span>

Combine the terms on the left:

\(\frac{\sin^3 \theta}{\cos^3 \theta} = \frac{q^3}{p^3}\)< /span>

We know that \(\tan \theta = \frac{\sin \theta}{\cos \theta}\)< /span>, so \(\tan^3 \theta = \frac{\sin^3 \theta}{\cos^3 \theta}\)< /span>. Therefore:

\(\tan^3 \theta = \frac{q^3}{p^3}\)< /span>

To find \(\tan \theta\)< /span>, we take the cube root of both sides:

\(\tan \theta = \sqrt[3]{\frac{q^3}{p^3}}\)< /span>

\(\tan \theta = \frac{q}{p}\)< /span>

Conclusion

By simplifying the given equations for \(\operatorname{cosec} \theta - \sin \theta\)< /span> and \(\sec \theta - \cos \theta\)< /span>, and then dividing them, we successfully derived the value of \(\tan \theta\)< /span>. The value of \(\tan \theta\)< /span> is \(\frac{q}{p}\)< /span>.

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Similar Questions

  1. What is the ratio of the greatest to the smallest value of 2 – 2 sin x – sin 2x, 0 ≤ x ≤ (π/2)? 

  2. What is (1 + cot θ - cosec θ)(1 + tan θ + sec θ) equal to?

  3. How many values of θ will satisfy the equation (sin2θ - 4 sin θ + 3) (4 - cos2θ + 4 sin θ) = 0, where 0 < θ < \(\frac{\pi}{2}\) ?

  4. If 7 sin4 θ + 9 cos4 θ + 42 sin2 θ = 16, 0 < θ < \(\frac{\pi}{2}\), then what is tan θ equal to ?

  5. If sin θ + cos θ = √2, then what is sin 6 θ + cos 6 θ + 6 sin 2 θ cos 2 θ equal to?

  6. If cos θ + sec θ = k, then what is the value of sin 2θ - tan 2θ ?

  7. Consider the following statements:

    1. The value of cos 61° + sin 29° cannot exceed 1.

    2. The value of tan 23° - cot 67° is less than 0.

    Which of the above statements is / are correct?

  8. Consider the following statements:

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    2. tan θ + cot θ cannot be less than 2, where 0 < θ <  \(\frac{\pi}{{2}}\)

    Which of the above statements is / are correct?

  9. If cos 47° + sin 47° = k, then what is the value of cos 2 47° - sin 2 47°?

  10. If cosec θ - cot θ = m, then what is cosec θ equal to?


Important Questions from Trigonometric Ratios and Identities

  1. What is the ratio of the greatest to the smallest value of 2 – 2 sin x – sin 2x, 0 ≤ x ≤ (π/2)? 

  2. If sinθ = \(\frac{4}{5}\) , Find the value of sin3θ

  3. If x, y are acute angles, where 0 < x + y < 90° and sin(3x - 40°) = cos (3y + 40°), then the value of tan (x + y) is equal to

  4. What is (1 + cot θ - cosec θ)(1 + tan θ + sec θ) equal to?

  5. If cos x = p/q and 0° < x < 90°, then the value of tan x is:

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