For the construction of the three-dimensional surface ensional surface **F(x,y)** in Mathcad, the function is preliminary assigned as matrix **М** of ordinates ** F(x,y)**. The sample plot appears, the left upper corner of which is where the cursor is. The sample plot contains only one single entry field: a dark rectangle at the left lower corner of the main plot. The matrix M or the function **F** names are to be entered here in case of the automatic matrix construction. Geometric visualization of three-dimensional surfaces in Mathcad depends on a number of factors: image zoom, degree of rotation of the figure about the X and Y axes, algorithm of hidden lines cleanup application or denial, functional filling application, etc. In order to change these parameters in Mathcad it is advised to set the plot format. In order to construct three-dimensional surfaces and space figures one can use the scheme of parametric specifying of functions, which describe them. Figures are specified by the values of coordinates** х, у и z** of all the figure points. It should be mentioned that models of 3D –plots in Mathcad require three matrixes to be input, which contain arrays of coordinates:** X, Y и Z**. The programme listing shows the examples of surface plot construction.

Mathcad allows changing the default plot parameters. To do that one should open the dialogue box for 3D-plots formatting by double mouse clicking the field of the plot. The dialogue box ** 3-D Plot Format** сshows a number of flags to choose the plot construction mode and nine tabs:

- Backplanes;
- Special;
- Advanced;
- QuickPlotData;
- General;
- Axes;
- Appearance;
- Lighting;
- Title.

Let us discuss just one tab, which is shown in the picture, - General. The first set of numbers in section **View** shows **Rolation** , **Tilt** , **Twist**, **Zoom**, , it is possible to observe the already constructed surface plot below. Furthermore, in section **Axes Style** one can observe a number of switch keys and a flag to choose the style of plot dimensions imaging.

- Perimetr – shows the plot with its perimeter dimensions;
- Corner – shows the plot with its axes dimensions;
- None – shows the plot without its perimeter and axes dimensions;
- Equal scales – sets equal scales of axes;
- Frames – determines plot frame;
- Border – shows plot borders;
- Show Box – shows plot in form of parallelepiped. Switch bar
**Plot 1**allows choosing one of the forms of 3D-plot imaging. While working with setup settings it is possible to have a look at the result of the change of the image parameter without closing the setup bar. Just click the “Apply” button. If you want to get back to the document, click “OK”.

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