Contents
# Equation Database

Math Touch includes a database of hundreds of common equations. You insert them into the canvas by tapping the insert button, then, "Equations" then navigate through the categories and subcategories. When you have found the equation you want, tap the insert button to the right of the equation and the equation will be inserted into the canvas.
# Editing Equations

To edit an equation to change a symbol name, or description, navigate to the equation in the above-mentioned equation database, then tap on the equation itself instead of the insert button. The equation editor is displayed. Tap on a symbol and the information area will change to reflect your selection. You can tap in the symbol subscript or description text areas to edit them. To change the description of the equation, tap the "=" mark, and information about the equation will be displayed.
# Creating new Equation

To create a new equation, navigate to the category you want the equation to be in, then tap the "Edit" button, followed by the "+" button. You will have the option to create a new equation or category. Once you select "New Equation" you will be taken to the equation editor where a new equation and dummy variables will be set up. If you long press in the equation area just outside the equation itself, you will get a "Paste" button which will paste in the last equation you copied.
## Setting variable properties

To set the symbol, subscript, description, dimension or constant value of a variable, tap the variable. The information area will reconfigure to display information relevant to the item you have selected. If you want to turn a symbol into a vector, or back to a scalar, tap the Vector tab, and choose the vector button on the left of the vector toolbar. If you have selected a scalar symbol, it will become a vector, and if you have selected a scalar, it will become a scalar.
## Dimensional Analysis

Math Touch will perform a dimensional analysis on all equations whenever a change is made. The dimensional information is always displayed. When a symbol is selected, the dimension button reflects your choice for the dimension of the symbol. Tapping it brings up the dimension database to allow you to select a different dimension. When any other mathematical function is selected, the dimension button reflects the analyzed dimension, named if possible, or it will display a short warning. Tapping the warning will display more information about the problem, and highlight in red the symbols or math functions that cause the problem. You can use this information to correct your mistakes.

Math Touch will require that your dimensional analysis checks out before you save your changes. If there is a warning about the dimensional analysis, Math Touch will let you save your equations as a "draft." Draft equations are saved in the database so you can edit them later, but they are listed with a red background, and may not be inserted in the canvas.

You can circumvent Math Touch's requirement that all equations pass dimensional analysis by not specifying the dimension of one or more symbols. This is potentially an un-safe mode, use it only if you are sure you know what you are doing. In general, Math Touch's dimensional analysis will point you towards errors.
## Vector Analysis

The only difference between the dimensional analysis and vector analysis is that you may not circumvent vector analysis by leaving the symbols unspecified. In version 1, every symbol is either a scalar or vector. Vectors are notated by an over-half-harpoon. Please note that for multiplication to be defined for vectors, you must use the correct multiplication function. While the scalar multiplication (available on the Arithmetic tab) works if you are multiplying a string of scalars by a single vector, if you have multiple vectors, you must use the dot or cross multiplication buttons on the Vector tab's toolbar. Both the dot and cross product functions allow exactly two operands. You may not use vectors as exponents, nor may you place vectors in the denominator. In version 1, Math Touch does not reduce the overall equation to determine if the denominator is a vector, it simply checks if each division function's denominator resolves to a vector. In addition, you may not use a non-integer exponent when raising vectors to powers.
## Adding Mathematical Operators

Unlike other math applications, you do not type equations, you build them up graphically. The available math operators are categorized into three groups: "Arithmetic", "Vectors" and "Trig" which listed on the tabbar at the bottom of the equation editor. The fourth tab "Select" is used to navigate through the math expression and for the delete button.

To make simple additions to the eqation, simply select a symbol, then tap one of the math operators, the selected symbol will become the argument of the function, and if the function typically requires another arugment, a dummy symbol will be created. The selection is not limited to a symbol. You may select a function by tapping with two fingers; whichever function contains both of your touches will be selected. You may also use the first four buttons in the "Select" tab's toolbar to precisely navigate your expression. You do not need to enter parenthesis, they will be created for you where they are necessary to visually indicate the order of operations. This will also help you confirm you have entered the equation correctly.

You may notice that unlike typical equation entry, some things are different. Suppose you wanted to enter a b + c d, you would start with the highest operation "+", then select each term in turn, and press the multiplication button. In linear entry on another product, you would have started with a b then pressed "+". If you do create "a b" first, just use the "up" button in the "Select" tab's toolbar to select the product of "a b" instead of just "b" when you press "+".
## Unsupported solutions

While all of the arithmetic and trig functions can perform inverse solutions, in general the vector operations do not work as inverse functions. There are some situations in which it is possible to use the direction and magnitude information of a vector to solve for the vector, but that behavior is not supported in version 1.
### A note about inverse tangent

On most other platforms, there is a difference between the inverse tangent function "arctan" or "atan" and the quadrant-correct inverse tangent, i.e. "atan2". In Math Touch, the arcTangent function intelligently selects whether the data provides for finding the correct quadrant: If the argument of the inverse tangent function is a division function, the correct-quadrant solution will be given. If the argument is a single symbol, even if linked from a division in another equation, the solution will be in the default quadrant.