Section 6: Functions continue97
Let’s work an example using LOG . The village of Musser has installed a 12-o’clock whistle in the firehouse steeple near the center of the village. If the sound level at the steeple (2.2. meters from the whistle) is 138 decibels, will resident near the edge of the town, three kilometers away, be able to hear the lunch whistle? The equation giving the sound level at the edge of town is:
 
  L = L0 – 20 log10 (r/r0)  
  L = 138 – [ 20 log10 (3000/2.2)]  
Where:
  L0 is the sound level at a point near the source (138 dB),
  r0 is the distance from the near point to the source (2.2 m),
  L is the sound level at a distant point, and
  r is the distance from the distant point to the source (3 km).
Keystrokes Display    
3000 ENTER  
– 3,000.0000    
   
2.2  ÷  
– 1,363.6364    
   
LOG 
– 3,1347    
   
20  ×  
– 62.6940    
   
CHS 
– 62.6940    
   
138  +  
– 75.3060    
  The sound level 3 kilometers from the firehouse is about 75 dB, well above the level of normal conversation.
The exponential Function
The Yx function ( Y^X if you execute it from the display), is used to raise numbers to powers. Using Yx permits you to raise a positive real number to any real power—that is, the power may be positive or negative, and it may be an integer, a fraction, or a mixed number. Yx also permits you to raise any negative real number to the power of any integer (within the calculating range of the calculator, of course).