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Question: Answered & Verified by Expert
If the sides of a triangle are in the ratio $2: \sqrt{6}: 1+\sqrt{3}$, then what is the smallest angle of the triangle?
MathematicsProperties of TrianglesNDANDA 2011 (Phase 2)
Options:
  • A $75^{\circ}$
  • B $60^{\circ}$
  • C $45^{\circ}$
  • D $30^{\circ}$
Solution:
2881 Upvotes Verified Answer
The correct answer is: $45^{\circ}$


Let $\mathrm{ABC}$ be a triangle with sides $\mathrm{a}=1+\sqrt{3}, \mathrm{~b}=2$ and
$c=\sqrt{6}$
So, $\cos B=\frac{a^{2}+c^{2}-b^{2}}{2 a c}=\frac{(1+\sqrt{3})^{2}+(\sqrt{6})^{2}-4}{2(1+\sqrt{3})(\sqrt{6})}$
$=\frac{2 \sqrt{3}+6}{2 \sqrt{6}+\sqrt{18}}=\frac{3+\sqrt{3}}{\sqrt{6}+3 \sqrt{2}}$
$=\frac{\sqrt{3} \sqrt{3}+\sqrt{3}}{(\sqrt{3}+\sqrt{3} \sqrt{3}) \sqrt{2}}=\frac{1}{\sqrt{2}}$
$\Rightarrow B=45^{\circ}$ is the smallest angle.
$(\because$ smallest side is $b=2$ )

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