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Trigonometric Functions — Maths STD 12 Science — Question

Maharashtra BoardEnglish MediumSTD 12 ScienceMathsTrigonometric Functions2 Marks
MCQ
In triangle ABC , $(b+c) \cos A+(c+a) \cos B+(a+b) \cos C=$
  • A
    $0$
  • B
    $1$
  • ✓
    $a+b+c$
  • D
    $2(a+b+c)$
✓

Answer

Correct option: C.
$a+b+c$
(C) $(b+c) \cos A+(c+a) \cos B+(a+b) \cos C$ $= a + b + c$
$=(b \cos C+c \cos B)+(c \cos A+a \cos C)$ $+(a \cos B+b \cos A)$
$=a+b+c \quad \ldots .[$ By projection rule $]$

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