Q90 / 150 · MHT CET 2022 (11 Aug Shift 1) · Mathematics

In a triangle $A B C$ with usual notations, If $a: b: c=7: 8: 9$ : then $\cos A: \cos B: \cos C=$

  • Correct answer
    A
    14:11:6
  • B
    7:8:9
  • C
    3:4:5
  • D
    5:6:7

Solution

Let $a=7 k, b=8 k, c=9 k$ Using cosine rule $\cos A=\frac{2}{3}, \cos B=\frac{11}{21}, \cos C=\frac{2}{7}$ $Rightarrow \cos A: \cos B: \cos C=14: 11: 6$

Hence, the correct answer is option: 'A'.

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