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MHT CET · Maths · Properties of Triangles

If the lengths of the sides of triangle are \(3,5,7\), then the largest angle of the triangle is

  1. A \(\frac{\pi}{2}\)
  2. B \(\frac{5 \pi}{6}\)
  3. C \(\frac{2 \pi}{3}\)
  4. D \(\frac{3 \pi}{4}\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(\frac{2 \pi}{3}\)

Step-by-step Solution

Detailed explanation

Let \(\mathrm{a}=3, \mathrm{~b}=5, \mathrm{c}=7 \)
\( \cos \mathrm{C}=\frac{\mathrm{a}^2+\mathrm{b}^2-\mathrm{c}^2}{2 \mathrm{ab}}=\frac{9+25-49}{2 \times 3 \times 5}=\frac{-15}{30}=-\frac{1}{2} \)
\( \therefore \angle C=\frac{2 \pi}{3}\)