Eliminating Absolute Values |
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Use Assumptions is a drop down list in the output Display Properties dialog box that determines whether expressions include or eliminate absolute values: the assumption in question is whether the operand of the absolute value is positive or negative. ![]() When set to True, the application assumes that a given term is positive, if the value of the absolute value operand is positive. If it’s negative, the corresponding term is assumed to be negative. When set to False, pertinent terms appear in expressions enclosed in absolute value bars. For example, without assumptions, in this drawing of Paucellier’s linkage, the height of D depends on parameter t: ![]() If you set Use Assumptions to True, the expression simplifies and no longer involves t. However, other assumptions can sometimes be added, as shown below. Check these assumptions against the geometry of the diagram to see if they accurately express your intentions. ![]() The second assumption in the drawing above is equivalent to assuming that angle AEB is obtuse; given the geometry of the drawing, is reasonable. Assumptions are a means to simplify expressions and apply only to absolute values. If an expression doesn't include any terms in absolute values, the option will have no effect. |