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# CALC 1 Formula Calculators General Help

The CALC 1 formula calculators are dedicated to a single formula with store, recall and solve keys for each parameter as well as the result. You can also easily create a graph of the formula by entering the range and selecting the independent variable.

Formula calculators also provide a convenient way to use functions that have more than a few parameters. The Normal Distribution formula calculators are example of this case.

When there are more than 4 parameters a second row will appear, except when using the iPhone/iPod touch in landscape.

CALC 1 comes with many Formula Calculators and more can be easily downloaded. You can also create your own Formula Calculator.

## Using a Formula Calculator

For each formula calculator, you calculate the formula when you tap the left most key in the top row. Before this, you will want to store the independent variable values.

See the Percent Change Formula Calculator as an example.

The formula is

old+old*PctCh/100

So the calculator looks like this: There are keys for the independent values, old, Δ% and the result, new.

To calculate the new value, you enter values for old and Δ% by tapping

123 then

20 then tap for a result of 147.6000.

## Solving for Independent Variables

The CALC 1 formula Calculators will also solve for most independent variables. So for the Percent Change Formula Calculator we want to calculate the Δ% for a new value of 150.

150 Then Calculates the PctCh value of 21.9512.

This is called solving. With solving, CALC 1 starts with the initial guess. In this example the initial guess is 20. The solver then calculates the formula using the initial guess and compares it to the target. In this example the goal is 150. The solver then determines if it should increase or decrease the initial guess to find the value of "Δ%" that will give you the target value.

In the 2nd Degree Polynomial example, there are 2 values for X that will result in Fx=0. Which root that is calculated depends on the initial guess you provide to the solver.

When you attempt to solve for an independent variable and get an error message, "Unable to bracket the initial guess" this means that the solver was not able to find two values for the independent variable that resulted in a value greater than and less than the target. Check and make sure that what you are solving for is possible. In the Cumulative Distribution Function for 2 Values example 2, if you tried to find a value for x2 that resulted in a cdf of .99, you would get this error. That is because, given the value of x1, it is not possible to have a value for x2 that has a cdf of .99.

Sometimes, changing your initial guess will help find a solution.

In all of our examples we begin by calculating the dependent variable. Then small changes in the dependent variable will usually give you the answer you are looking for for the independent variable.

In general, CALC 1, like most calculators that solves for roots will work best with continuous functions.

## Graphing

CALC 1 will easily create a graph of the formula (function) of any Formula Calculator.

In general, you enter the minimum and maximum value for the independent variable, tap shift and select the independent variable.

The Polynomial 3 Formula Calculator has a graphing example.

## Create Your Own Formula Calculator

You can create your own Formula Calculator by entering a spreadsheet formula and the labels for the keys.

## Customizing the Keys

In a Formula Calculator, the top row (or top two rows for more than 4 independent variables) are used for the formula. The remaining keys behave just like a Focused Calculator so you can copy, paste and edit these keys.

To access the Calculator Editor for the Formula Calculators, tap the edit icon at the bottom of the Formula Calculators list.