Let x be a real number between 0 and π. Provide an expression for tan²(x) which does not involve any trigonometric functions.
a) (1 - cos²(x))/(cos²(x)).
b) (1 - sin²(x))/(cos²(x)).
c) sin²(x)/cos²(x).
d) cos²(x)/(1 - sin²(x)).