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TS EAMCET · Maths · Properties of Triangles

In a triangle ABC , if \(r_1=6, r_2=9, r_3=18\), then \(\cos \mathrm{A}=\)

  1. A \(\frac{5}{13}\)
  2. B \(\frac{4}{5}\)
  3. C \(\frac{5}{7}\)
  4. D \(\frac{7}{25}\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(\frac{4}{5}\)

Step-by-step Solution

Detailed explanation

\(\frac{\Delta}{s-a}=6 \Rightarrow s-a=\frac{\Delta}{6}\) ...(i) \(\frac{\Delta}{s-b}=9 \Rightarrow s-b=\frac{\Delta}{9}\) ...(ii) \(\frac{\Delta}{s-c}=18 \Rightarrow s-c=\frac{\Delta}{18}\) ...(iii) Adding (i), (ii) and (iii)…