Question

With usual notation, in a triangle ABC $\frac{b+c}{11} = \frac{c+a}{12} = \frac{a+b}{13}$, then the value of $\cos B$ is equal to

• A. $\frac{17}{35}$
• B. $\frac{17}{70}$
• C. $\frac{19}{35}$
• D. $\frac{19}{70}$

Hint:

In ratio problems, use a constant $k$ to represent side lengths and then apply standard triangle formulae.

Answer 1

The Correct Option is C