Although some people may be confused at the sight of Burt Lancaster playing a native American, in fact, Thorpe himself was not a full-blooded Native American, being part Irish on his mother's side.
At the Carlisle Indian School, when we first see Jim at the blackboard, he is erasing a formula: I = E/R. This is Ohm's law (1827), in which, in an electrical circuit, you can determine I (current, in amps), E (voltage, in volts), or R (resistance, in ohms) by knowing two of the three values.