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If sin 3A = cos (A – 10°) and 3A is acute then A =?

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Question

If sin 3A = cos (A – 10°) and 3A is acute then A =?

Options

  • 15°

  • 20°

  • 25°

  • 30°

MCQ
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Solution

25°

Explanation:

sin 3A = cos (A – 10°) 

⇒ cos (90° – 3A) = cos (A – 10°) 

⇒ 90° – 3A = A – 10° 

⇒ 4A = 100° 

⇒ A = 25°

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Chapter 12: Trigonometric Ratios of Some Complemantary Angles - MULTIPLE-CHOICE QUESTIONS (MCQ) [Page 594]

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R.S. Aggarwal Mathematics [English] Class 10
Chapter 12 Trigonometric Ratios of Some Complemantary Angles
MULTIPLE-CHOICE QUESTIONS (MCQ) | Q 20. | Page 594
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