अंतराल [0, π] में आने वाले समीकरण sin x + sin 5x = sin 3x के हलों की संख्या क्या है?

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NIMCET 2018 Official Paper
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  1. 4
  2. 6
  3. 5
  4. 2

Answer (Detailed Solution Below)

Option 2 : 6
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NIMCET 2020 Official Paper
120 Qs. 480 Marks 120 Mins

Detailed Solution

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संकल्पना:

  • sin (A ± B) = sin A cos B ± sin B cos A.
  • sin 2A + sin 2B = 2 sin (A + B) cos (A - B).
  • cos (2nπ + θ) = cos θ.

 

गणना:

sin x + sin 5x = sin 3x

sin 2A + sin 2B = 2 sin (A + B) cos (A - B) का प्रयोग करने पर, हमें निम्न प्राप्त होता है:

2 sin 3x cos 2x = sin 3x

⇒ sin 3x (2 cos 2x - 1) = 0

⇒ sin 3x = 0 या 2 cos 2x - 1 = 0

स्थिति 1: sin 3x = 0 = sin nπ, n ∈ Z.

⇒ 

⇒ 

स्थिति 2: 2 cos 2x - 1 = 0

⇒ , n ∈ Z.

⇒ 

⇒ 

इसलिए, अंतराल [0, π] में x के 6 संभव मान हैं। 

 

Additional Information

संबद्ध कोणों के लिए त्रिकोणमितीय अनुपात: ​ 

  • sin (-θ) = -sin θ
  • cos (-θ) = cos θ
  • sin (2nπ + θ) = sin θ
  • cos (2nπ + θ) = cos θ
  • sin (nπ + θ) = (-1)n sin θ
  • cos (nπ + θ) = (-1)n cos θ
  •  = (-1)n cos θ
  •  = (-1)n (-sin θ)

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