Section 6: Functions80
Y-register, the y value is divided by x and the remainder is placed back into the X-register. For example, find 128 modulo 10:
Keystrokes Display    
128 ENTER  
  128.0000    
  The y-value.
10
  10 _    
  The x-value.
XEQ 
  XEQ _ _    
   
ALPHA MOD ALPHA 
  8.0000    
  The value is in X.
Performing y mod x when x=0 returns an answer of 0.
Reciprocals
To calculate the reciprocal of a number in the X-register, key in the number, then execute the 1/x (reciprocal) function. For example, to calculate the reciprocal of the number 1.7588028 × 1011 (the electron charge-to-mass ratio):
Keystrokes Display    
1.7588028 EEX 11
  1.7588028 – 11
  The number.
1/x 
  5.6857 – 12
  The reciprocal.
You can also calculate the reciprocal of a value in a previous calculation without reentering the number.
Example: In an electric circuit, three resistors are connected in parallel and a single resistor is connected in series with the parallel circuit. The resistors in parallel have values of 2.7 kilohms, 5.6 kilohms, and 7.5 kilohms, and the series resistor has a value of 680 ohms. What is the total resistance of the circuit?
      1       1    
  Rt =
 
+ R4 =
 
+  680
     
1 + 1 + 1
 
 
 
R1 R2 R3
     
1 + 1 + 1
 
 
 
2700 5600 7500
   
Keystrokes Display    
2700 1/x 
  0.0004    
   
5600 1/x 
  0.0002    
   
 +  
  0.0005    
   
7500 1/x 
  0.0001    
   
 +  
  0.0007    
  Sum of the reciprocals.
1/x 
  1,465.6844    
  The reciprocal of the sum of the reciprocals.
680  +  
  2,145.6844    
  Addition of the series value yields the answer in ohms.