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Trigonometric Functions — Maths STD 12 Science — Question

Maharashtra BoardEnglish MediumSTD 12 ScienceMathsTrigonometric Functions2 Marks
MCQ
In $\triangle A B C, \frac{\cos A}{a}+\frac{\cos B}{b}+\frac{\cos C}{c}=$
  • A
    $\frac{a^2+b^2+c^2}{a b c}$
  • ✓
    $\frac{a^2+b^2+c^2}{2 a b c}$
  • C
    $\frac{2\left( a ^2+ b ^2+ c ^2\right)}{ abc }$
  • D
    $a^2+b^2+c^2$
✓

Answer

Correct option: B.
$\frac{a^2+b^2+c^2}{2 a b c}$
(B) $\frac{\cos A}{a}+\frac{\cos B}{b}+\frac{\cos C}{c}$
$=\frac{ b ^2+ c ^2- a ^2+ a ^2+ c ^2- b ^2+ a ^2+ b ^2- c ^2}{2 abc }$
$=\frac{ a ^2+ b ^2+ c ^2}{2 abc }$

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