cot (A - B) = \(\rm \frac{\cot A\cot B+1}{\cot B-\cot A}\) ব্য়বহার করে, cot 15° এর মান নির্ণয় করুন।

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Question

This question was previously asked in

SSC CGL 2023 Tier-I Official Paper (Held On: 19 Jul 2023 Shift 2)

Answer 1

গণনা:

cot (A - B) = \(\rm \frac{\cot A\cot B+1}{\cot B-\cot A}\)

⇒ Cot15° = Cot(45° - 30°)

⇒ Cot(45° - 30°) = Cot45°Cot30° + 1/Cot30° - Cot45°

⇒ 1 × √3 + 1/√3 - 1

⇒ √3 + 1/√3 - 1

⇒ √3 + 1/√3 - 1 × √3 + 1/√3 + 1

⇒ (√3 + 1)²/2

⇒ (3 + 1 + 2√3)/2

⇒ (2√3 + 4)/2

⇒ √3 + 2

∴ সঠিক উত্তর হল √3 + 2

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