If cos3A = sin (A - 18o), where 3A is an

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Target Exam

CUET

Subject

General Test

Chapter

Quantitative Reasoning

Topic

Trigonometry

Question:

If cos3A = sin (A - 18^o), where 3A is an acute angle, what is the value of A ?

Options:

110^o

108^o

54^o

27^o

Correct Answer:

27^o

Explanation:

cos3A = sin ( A - 18º)

{ Using , If sinA = cosA then A + B = 90º }

So, 3A + A - 18º = 90º

4A = 108º

A = 27º