Practicing Success

Target Exam

CUET

Subject

General Test

Chapter

Quantitative Reasoning

Topic

Trigonometry

Question:

If 2 sin2θ + 3 cosθ = 3, 0o < θ < 90o, then the value of (sec2θ +cot2 θ) is 

Options:

$3\frac{2}{3}$

$3\frac{1}{3}$

$4\frac{1}{3}$

$4\frac{1}{2}$

Correct Answer:

$4\frac{1}{3}$

Explanation:

We are given that :-

2 sin²θ + 3 cosθ = 3

{ we know, sin²θ + cos²θ = 1 }

2 ( 1 - cos²θ ) + 3 cosθ = 3

2 - 2cos²θ + 3 cosθ = 3 

2cos²θ - 3 cosθ + 1 = 0 

2cos²θ - 2 cosθ  - cosθ + 1 = 0

2 cosθ ( cosθ - 1 ) - 1 ( cosθ - 1 ) = 0

( 2cosθ - 1 ) . ( cosθ - 1 ) = 0

( cosθ - 1 ) = 0  is not possible because 0º < θ < 90º

So, 2cosθ - 1 = 0

cosθ = \(\frac{1}{2}\)

{ we know, cos60º = \(\frac{1}{2}\) }

So,  θ = 60º

Now,

( sec ²θ + cot ²θ )

= ( sec ²60º + cot ²60º ) 

= 4 + \(\frac{1}{3}\)

= 4\(\frac{1}{3}\)