HP 35s User Manual

 
hp calculators 
 
HP 35s  Using the formula solver – part 1 
 
hp calculators - 5 - HP 35s  Using the formula solver – part 1- Version 1.0 
 Figure 7 
 
 This shows that it can be very important to begin with a good guess. Obviously, only positive numbers 
should be used in the search for a solution this time. To make sure that only positive numbers are used in 
the search, two guesses can be given. One is the number in the variable being solved for. The other is the 
number displayed in the lower line...

 
hp calculators 
 
HP 35s  Using the formula solver – part 1 
 
hp calculators - 6 - HP 35s  Using the formula solver – part 1- Version 1.0 
 Figure 11 
  
 The number in x is the best answer, the number in y, shown in Figure 11, is the previous value, and the 
number in z is the value of the formula. Use the left and right arrow keys to see each of these numbers, 
and press 3 to copy the number shown into a calculation. 
  
 If the numbers in stack registers X and Y differ by 1 in the last digit then...

 
hp calculators 
 
HP 35s  Using the formula solver – part 1 
 
hp calculators - 7 - HP 35s  Using the formula solver – part 1- Version 1.0 
What the Solver can and can not find 
 
The examples above have shown the basics of what the formula solver can find and what it can not find. 
 
In a formula or equation with one unknown variable the solver can find one or more roots if there are any. 
  
If the solution can not be represented exactly, the solver finds the two nearest numbers on either side of it....

 
 
hp calculators 
 
 
 
 
HP 35s  Using the formula solver – part 2 
 
 
 
 
Overview of the formula solver 
 
Practice Example: A formula with several variables 
 
Practice Example: A direct solution 
 
Practice Example: Where two functions intersect 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
   

 
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HP 35s  Using the formula solver – part 2 
 
hp calculators - 2 - HP 35s  Using the formula solver – part 2 - Version 1.0 
Overview of the Formula Solver 
 
Given an expression of the form: 
 
f(x) = y 
 
The HP Solve Application searches for a value of x that gives: 
 
f(x) = y = 0 
 
A value of x for which this is true is called a root, and it provides a solution of the equation f(x) = 0. The graph in 
Figure 1 shows this graphically – there is a root at the value of x where f(x) is...

 
hp calculators 
 
HP 35s  Using the formula solver – part 2 
 
hp calculators - 3 - HP 35s  Using the formula solver – part 2 - Version 1.0 
If a direct solution is not found, the Solver begins by first trying two guesses for the unknown variable. The user can give 
one or two guesses for the Solver to start from. The first part showed that this can be very useful, either to direct the 
Solver towards one root of several, or to direct the Solver away from values that would cause an error. Good guesses...

 
hp calculators 
 
HP 35s  Using the formula solver – part 2 
 
hp calculators - 4 - HP 35s  Using the formula solver – part 2 - Version 1.0 
Practice Example: A formula with several variables 
 
Example 1:  A factory is to produce tin cans with a volume of 100 cubic centimeters. The designer estimates that the 
height should be 10 cm and the radius about 2 cm. Calculate the exact volume of this can, and if it is not 
close to 100 cubic centimeters then recalculate the radius to give the required...

 
hp calculators 
 
HP 35s  Using the formula solver – part 2 
 
hp calculators - 5 - HP 35s  Using the formula solver – part 2 - Version 1.0 
 The Solver asks for the other known variable. Type the height, 10, and press 1 again. The HP 35s 
displays SOLVING for a moment, then the result. 
  
 Figure 6 
  
 The volume is over 125 cubic centimeters, considerably more than the intended 100. Repeat the 
calculation, but this time use the known volume of 100, and solve for the radius. Solve the equation...

 
hp calculators 
 
HP 35s  Using the formula solver – part 2 
 
hp calculators - 6 - HP 35s  Using the formula solver – part 2 - Version 1.0 
 Figure 10 
  
 To solve the equation, press -03. The Solver immediately displays the answer: 
  
 Figure 11 
  
Answer: Z = 1 is the solution to LN(z) = 0. This is obvious, the point of this example is that the answer was found 
immediately, and the negative guess was not tried. If the negative guess had been tried, it would have 
caused a LOG(NEG) error, as in...