Computes the `[m/n]` Padé approximant of a function about a point: the rational
PadeApproximant[expr, {x, x0, {m, n}}]
PadeApproximant[expr, {x, x0, n}]
PadeApproximant[Exp[x], {x, 0, {2, 2}}]
→ (1 + x/2 + x^2/12)/(1 - x/2 + x^2/12)PadeApproximant[Cos[x], {x, 0, {2, 2}}]
→ (1 - (5*x^2)/12)/(1 + x^2/12)PadeApproximant[Log[1 + x], {x, 0, {2, 2}}]
→ (x + x^2/2)/(1 + x + x^2/6)PadeApproximant[ArcTan[x], {x, 0, {3, 2}}]
→ (x + (4*x^3)/15)/(1 + (3*x^2)/5)PadeApproximant[Exp[x], {x, 0, {2, 0}}]
→ 1 + x + x^2/2