Analog Input. In this example we use a variable resistor (a potentiometer or a photoresistor), we read its value using one analog input of an Arduino or Genuino board and we change the blink rate of the built-in LED accordingly. The resistor's analog value is read as a voltage because this is how the analog inputs work.
For the Haigis formula, the a0 constant moves the power prediction curve up, or down, in much the same way that the SRK/T A-constant. The a1 constant is tied to the measured anterior chamber depth and the a2 constant is tied to the measured axial length.
The three sides of a right triangle are represented by the variables a, b, and c. The variable c always represents the longest side. You can write the formula used above as . This is the formula of the Pythagorean Theorem. The longest side of a right triangle is always directly across from the 90 degree angle.