Classical kinetic energy:
Ke = mv2/2
Relativistic kinetic energy equation:
Ke = mc2(1 / sqr(1 - (v/c)2) - 1)
The taylor series for this:
Ke = mv2/2 + 3mv4/(8c2) + 5mv6/(16c4) + 35mv8/(128c6) + . . .
A trigonometrical equation for:
Ke = mc2(1 / (1 / ((v/c) tan ((arc sin (v/c))/2)) - 1)
And the algebraic form:
Ke = mv2/(1 + sqr(1 - (v/c)2) - (v/c)2)