Practicing Success

Target Exam

CUET

Subject

General Test

Chapter

Quantitative Reasoning

Topic

Trigonometry

Question:

Solve for $θ : 3 cosec θ + 4sin θ - 4 \sqrt{3} = 0, $ where θ is an acute angle.

Options:

45°

30°

60°

15°

Correct Answer:

60°

Explanation:

3 cosecθ  + 4 sinθ  - 4√3 = 0

3 × \(\frac{1}{sin θ}\)  + 4 sinθ  - 4√3 = 0

3  + 4 sin²θ  - 4√3 sinθ = 0

 4 sin²θ  - 2√3 sinθ- 2√3 sinθ + 3  = 0

2sinθ ( 2sinθ - √3 ) - 1 ( 2sinθ - √3 ) = 0

( 2sinθ - √3 ) ( 2sinθ - 1 ) = 0

Either 2sinθ - √3  = 0 OR 2sinθ - 1 = 0

2sinθ - 1 = 0   is not possible because θ is an acute angle triangle.

So, 2sinθ - √3  = 0 

sinθ = \(\frac{√3}{2}\)

{ we know,  sin60º = \(\frac{√3}{2}\) }

so, θ = 60º