Practicing Success

Target Exam

CUET

Subject

General Test

Chapter

Quantitative Reasoning

Topic

Trigonometry

Question:

If 5sin2 θ = 3(1 + cosθ), 0° < θ < 90°, then the value of cosecθ + cotθ is :

Options:

$\frac{4}{\sqrt{21}}$

$\sqrt{\frac{3}{7}}$

$\frac{5}{\sqrt{21}}$

$\sqrt{\frac{7}{3}}$

Correct Answer:

$\sqrt{\frac{7}{3}}$

Explanation:

5sin2 θ = 3(1 + cosθ)

{ sin2 θ + cos2 θ  = 1 }

5 ( 1 - cos2 θ) = 3(1 + cosθ)

5 ( 1 - cos θ) = 3

cos θ = \(\frac{2}{5}\)

By using pythagoras theorem ,

P2 + B2 = H2

P2 + 22 = 52

P = \(\sqrt {21 }\)

ATQ,

 cosecθ + cotθ

= \(\frac{5}{√21}\) + \(\frac{2}{√21}\)

= \(\frac{7}{√21}\)

= \(\frac{√7}{√3}\)