Practicing Success

Target Exam

CUET

Subject

General Test

Chapter

Quantitative Reasoning

Topic

Trigonometry

Question:

If $\frac{2cos^3 A - cosA}{sinA - 2 sin^3 A}$ = 1$, then what is the value of A ?

Options:

90o

30o

45o

60o

Correct Answer:

45o

Explanation:

\(\frac{ 2cos³A - cosA}{sinA - 2sin³A}\) = 1

\(\frac{ cosA( 2cos²A - 1)}{sinA( 1 - 2sin²A)}\) = 1

{ we know that, 2cos²A - 1 = cos2A  and  1 - 2sin²A = sin2A }

\(\frac{ cosA.cos2A}{sinA.sin2A}\) = 1

\(\frac{ cosA}{sinA}\) = 1

cotA = 1

{ using cot45º = 1 }

So, A = 45º