If sinθ + cosθ = √2, then what is the value of 8 sinθ cosθ?

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DFCCIL Executive CBT1 Electrical 25 Aug 2023 Shift 2 Official Paper
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  1. 2
  2. 16
  3. 8
  4. 4

Answer (Detailed Solution Below)

Option 4 : 4
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Detailed Solution

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Given:

If sinθ + cosθ = √2

Formula used:

(sinθ + cosθ)2 = sin2θ + cos2θ + 2sinθcosθ

Calculation:

(sinθ + cosθ)2 = (√2)2

⇒ sin2θ + cos2θ + 2sinθcosθ = 2

We know that sin2θ + cos2θ = 1

⇒ 1 + 2sinθcosθ = 2

⇒ 2sinθcosθ = 1

⇒ sinθcosθ = 1/2

⇒ 8sinθcosθ = 8 × 1/2 = 4

∴ The correct answer is option (4).

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