If `cos 27^\circ = x`, then the value of `tan 63^\circ` is -
(a) `\frac{\sqrt{1-x^2}}{x}`, (b) `\frac{x}{\sqrt{1-x^2}}`, (c) `\frac{x}{\sqrt{1+x^2}}`, (d) `\frac{x}{\sqrt{x^2-1}}`