MCQ practice · SSC General Mathematics Board questions · Chapter 9: Trigonometric Ratio
If sin 3A = cosec 3A, what is A?
Think it through first, then pick an option.
- a 10°
- b 15°
- c 30°
- d 60°
Answer and explanation
Correct answer: c 30°
sin 3A = 1/sin 3A gives sin²3A = 1; 3A = 90° so A = 30°.
Why the other options are wrong
- a 10°: A = 10° gives 3A = 30°: sin 30° = 1/2 and cosec 30° = 2, not equal.
- b 15°: A = 15° gives 3A = 45°: sin 45° = 1/√2 and cosec 45° = √2, not equal.
- d 60°: A = 60° gives 3A = 180°, which is not acute, and sin 180° = 0.
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