If in a triangle ABC, sinA4=sinB5=sinC6, then the value of cosA+co | Filo
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Class 12

Math

Trigonometry

Trigonometric Functions

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If in a triangle ABC, sinA4=sinB5=sinC6, then the value of cosA+cosB+cosCis equal to

  1. 6948
  2. 9648
  3. 4869
  4. None of these
Correct Answer: Option(a)
Solution: We have sinA4=sinB5=sinC6⇒a4=b5=c6=λ (say) ∴ a=4λ,b=5λ,c=6λ Now cosA+cosB+cosC = b2+c2−a22bc+c2+a2−b22ac+a2+b2−c22ab = 1240λ3{4λ(45λ2+5λ(27λ2)+6λ(5λ2)}=6948.
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