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# Functions, prefixes, and algebraic operators

Use Equations and Parameters

You can use equations wherever you can enter a numeric value. For example, you can write equations in the Edit Dimensions dialog box, feature dialog boxes, and the Parameters dialog box. Equations can vary in complexity, and you can use them to calculate feature sizes, calculate assembly constraints offsets or angles, or simulate motion among several components.

Equations can be simple or contain many algebraic operators, prefixes, and functions. For example, here is a simple equation:

2 ul *(6+3)

The following complex equation uses internal parameters such as pi:

Algebraic operators

The following table lists the algebraic operators supported by Autodesk Inventor.

 Operator Meaning + addition - subtraction % floating point modulo * multiplication / division ^ power ( expression delimiter ) expression delimiter ; delimiter for multi-argument functions

Unit prefixes

The following table lists the unit prefixes supported by Autodesk Inventor.

 Prefix Symbol Value exa E 1.0e18 peta P 1.0e15 tera T 1.0e12 giga G 1.0e9 mega M 1.0e6 kilo k 1.0e3 hecto h 1.0e2 deca da 1.0e1 deci d 1.0e-1 centi c 1.0e-2 milli m 1.0e-3 micro micro 1.0-6 nano n 1.0-9 Pi co p 1.0e-12 femto f 1.0-15 atto a 1.0e-18

When you use unit prefixes in an equation, enter the prefix symbol. Do not enter the prefix itself. For example, an equation that includes the unit "nanometer" might look like this equation: 3.5 ul * 2.6 nm.

When you add the unit prefix for name to the meter unit, your equation is calculated based on the length of 2.6 nanometers.

NotePrefix symbols are case sensitive. Enter them exactly as they appear in the previous table.

Functions

The following table lists the supported functions.

 Syntax Returns Unit Type Expected Unit Type cos(expr) unitless angle sin(expr) unitless angle tan(expr) unitless angle acos(expr) angle unitless asin(expr) angle unitless atan(expr) angle unitless cosh(expr) unitless angle tanh(expr) unitless angle acosh(expr) angle unitless asinh(expr) angle unitless sqrt(expr) unit^1/2 any sign(expr) unitless any (Return 0 if negative, 1 if positive.) exp(expr) unitless any (Return exponential power of expression: for example, return 2 for 100, 3 for 1000, and so on.) floor(expr) unitless unitless (Next lowest whole number.) ceil(expr) unitless unitless (Next highest whole number.) round(expr) unitless unitless (Closest whole number.) abs(expr) any any max(expr1;expr2) any any min(expr1;expr2) any any ln(expr) unitless unitless log(expr) unitless unitless pow(expr1;expr2) unit^expr2 any and unitless, respectively random(expr) unitless unitless isolate(expr;unit;unit) any any
NoteFunction names are case sensitive. Enter them exactly as they appear in the previous table.

Reserved system parameters

The following table lists the reserved system parameters supported by Autodesk Inventor.

 Parameter Value PI 3.14159265358979323846264338328 E 2.71828182845904523536

Unit types

The unit type that you use with an equation depends on the type of data that you are evaluating. For example, to evaluate a linear or angular value, you typically use a unit type of millimeters, inches, or degrees (mm, in, or deg).

Some equations must return a unitless value, for example, an equation to solve the number of occurrences in a pattern. You designate a unitless value with the characters ul. For example, 5 ul means that the equation has been evaluated and returned the number 5, as in the number of occurrences in a pattern.

NoteKeep units consistent within equations containing parameters that represent different unit types. You can do this using the Isolate function. For example, to calculate the number of occurrences for a pattern that is based on one occurrence for each unit of a parameter named Width, your linear equation would be:

isolate(Width;mm;ul)

The number of Occurrences value in a dialog box requires a unitless (ul) result, but you are referencing the unit width, which is a linear value. Convert the Width parameter to a unitless value.