Tip 26. Begin with a symbol but
finish by a number
Fig. 26.
Begin with a symbol but finish by a
number
In tip 24 we try to solve the system of algebraic equations using diagram method – we have defined the
domain of existence of real roots of the system, we have found the values of
the unknowns for first approximation for search of the solution using numerical method that will be done in tip
44. But it is possible and necessary to try to put
in a «symbol» in the line «graph – number». The main point of the tip is the
following. It is worth to apply tools
of symbolic mathematics of Mathcad for solution a problem before using numerical
method. Analytic solution of our system of two nonlinear algebraic equations
(see tip 24) with the help of Mathcad-operators solve and float is showed in the fig. 26. (Here we use
not one operator solve but the
couple solve – float as
since one operator solve often gives either very bulky answer or
nothing). All 24 roots are found but for of them (1, 6, 19 and 22[1]) are real ones. They are reflected
on the graph in tip 24.
Only five signs in fixed point part (see the
key float, 5) are outputted in the answer in the fig. 26.
By default (without the key float) 20 signs are outputted but their
maximum quantity is 250. (The command of the same name from the menu Symbolic (the command Solve on Variable) can give up to 4 000 signs in
fixed point part. However the command works only with the equations but not
with the systems of equations.)
The roots can be outputted in the form of
decimal fraction with floating point (0.043778) but not in the «scientific»
form (4.3778×10-2), if we enclose the
expression in the fig. 26 by cursor and press the key «=». After this it
is possible to format corresponding way already «numerical» answer (see also tip 3).