ExamBro
ExamBro
MHT CET · Maths · Properties of Triangles

In a triangle ABC , with usual notations if \(a=4, \mathrm{~b}=8, \angle \mathrm{C}=60^{\circ}\), then the value of \(\angle \mathrm{B}\) and the ratio \(\cos \mathrm{A}: \cos \mathrm{C}\) respectively are,

  1. A \(\frac{\pi}{4},~ 1: \sqrt{3}\)
  2. B \(\frac{\pi}{2},~ \sqrt{3}: 1\)
  3. C \(\frac{\pi}{2},~ 2: \sqrt{3}\)
  4. D \(\frac{\pi}{6},~ \sqrt{3}: 2\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(\frac{\pi}{2},~ \sqrt{3}: 1\)

Step-by-step Solution

Detailed explanation

\(c^2 = a^2 + b^2 - 2ab \cos C = 4^2 + 8^2 - 2(4)(8) \cos 60^\circ = 16 + 64 - 64(0.5) = 80 - 32 = 48\) \(c = \sqrt{48} = 4\sqrt{3}\)