Archive for: November, 2015

Systems of differential equations

The procedure for solving a coupled system of differential equations follows closely that for solving a higher order differential equation. In fact, you can think of solving a higher order differential equation as just a special case of solving a system of differential equations. Systems of first order differential equations To solve a system of first order differential…

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A note about function definitions

When you define a function, Mathcad does not try to evaluate it until you use it later on in the worksheet. If there is an error, the use of the function is marked in error, even though the real problem may be in the definition of the function itself. Figure 7-14 shows two examples of…

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Starting in manual mode

• Click “OK” to stop the calculations or “Cancel” to resume calculations. If you click “OK,” Mathcad displays a message on the message line to indicate that processing has been interrupted. The equation that was being processed when you pressed [Ese] is marked with an error message indicating that calculation has been interrupted. To resume…

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Solving Differential Equations

This chapter describes how to solve both ordinary and partial differential equations having real-valued solutions. Mathcad Standard comes with the rkfixed function, a general-purpose Runge-Kutta solver that can be used on nth order differential equations with initial conditions or on systems of differential equations. Mathcad Professional includes a variety of additional, more specialized functions for solving differential equations. Some of these…

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Controlling calculations

When you start Mathcad, you are in “automatic mode,” This means that Mathcad updates results in the worksheet window automatically. You can tell you’re in automatic mode because the word “Auto” appears in the message line, If you don’t want to wait for Mathcad to make computations as you edit, disable automatic mode by choosing…

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Using the solver effectively

This section provides some ideas on how to effectively exploit Mathcad’s ability to solve systems of simultaneous equations. Repeatedly solving an equation The techniques given thus far, while they are effective for solving a particular system of equations, are limited by two things: • Every time you use a Find, you must have the rest of the…

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Copying numerical results

You can copy a numerical result and paste it either elsewhere in your worksheet or into another application. This allows you to copy an array of numbers directly spreadsheet or database into Mathcad where you can take advantage of its free-form interface and its advanced mathematical tools, and vice versa. Once you’ve performed the necessary…

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Systems of equations

Mathcad lets you solve a system of up to fifty simultaneous equations in fifty unknowns. The first part of this section sketches the procedure. The remainder contains several examples as well as a discussion of some common errors. The method given here will always return numbers for the unknown variables. To see the unknowns in terms of the other…

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Evaluating expressions

To evaluate an expression, follow these steps: • Type an expression containing any valid combination of numbers, variables and functions. Any variables or functions in this expression should be defined earlier in the worksheet. • Press the “=” key. Mathcad computes the value of the expression and shows it after the equals sign. Whenever you…

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Recursive function definitions

Figure 7-4: The value of a user function depends on its arguments. Pro Mathcad supports recursive function definitions-you may define the value of a function in terms of a previous value of the function. As shown in Figure 7-5, recursive functions are useful for defining arbitrary periodic functions, as well as elegantly implementing numerical functions…

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