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If (sin θ + cosec θ)2 + (cos θ + sec θ)2 = k + tan2 θ + cot2 θ, then the value of k is equal to:1. 52. 73. 24. 9 |
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Answer» Correct Answer - Option 2 : 7 Given: (sin θ + cosec θ)2 + (cos θ + sec θ)2 = k + tan2 θ + cot2 θ Formula used: (a + b)2 = a2 + 2ab + b2 sin2 θ + cos2 θ = 1 sec2 θ - tan2 θ = 1 cosec2 θ - cot2 θ = 1 sin θ × cosec θ = 1 cos θ × sec θ = 1 Calculation: According to the question, sin2 θ + cosec2 θ + 2 × sin θ × cosec θ + cos2 θ + sec2 θ + 2 × cos θ × sec θ = k + tan2 θ + cot2 θ ⇒ 1 + cosec2 θ + 2 × 1 + sec2 θ + 2 × 1 = k + tan2 θ + cot2 θ ⇒ 5 + (cosec2 θ - cot2 θ) + (sec2 θ - cot2 θ) = k ⇒ 5 + 1 + 1 = k ⇒ k = 7 ∴ The value of k is 7. |
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