Cosine Ratio from Sine Ratios
Trigonometry
In triangle $ABC$, $\sin A:\sin B:\sin C = x:y:z$. Determine $\dfrac{\cos A}{\cos B}$ in terms of $x$, $y$, and $z$.
A$\frac{y(x^2+z^2-y^2)}{x(y^2+z^2-x^2)}$
B$\frac{x(y^2+z^2-x^2)}{y(x^2+z^2-y^2)}$
C$\frac{x(x^2+z^2-y^2)}{y(y^2+z^2-x^2)}$
D$\frac{x^2(y^2+z^2-x^2)}{y^2(x^2+z^2-y^2)}$