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The Maxima on-line user's manual

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Assume Calculator

Assume

Function: assume (<pred_1>, ..., <pred_n>) Adds predicates <pred_1>, ..., <pred_n> to the current context. If a predicate is inconsistent or redundant with the predicates in the current context, it is not added to the context. The context accumulates predicates from each call to assume.

assume(s > 0);
assume(m > 0);
t(x):=sqrt(2*((x*m)-0.21*m)/(-9.81*m/(s^2)));
i(x):=sin(t(x));
define(p(x),subst(1,s,i(x)));
plot2d((p(x)),[x,0,2000]);

assume returns a list whose elements are the predicates added to the context or the atoms redundant or inconsistent where applicable.

The predicates <pred_1>, ..., <pred_n> can only be expressions with the relational operators < <= equal notequal >= and >. Predicates cannot be literal equality = or literal inequality # expressions, nor can they be predicate functions such as integerp.

Compound predicates of the form <pred_1> and ... and <pred_n> are recognized, but not <pred_1> or ... or <pred_n>. not <pred_k> is recognized if <pred_k> is a relational predicate. Expressions of the form not (<pred_1> and <pred_2>) and not (<pred_1> or <pred_2>) are not recognized.

Maximas deduction mechanism is not very strong; there are many obvious consequences which cannot be determined by is. This is a known weakness.

assume does not handle predicates with complex numbers. If a predicate contains a complex number assume returns inconsistent or redunant.

assume evaluates its arguments.

See also is, facts, forget, context, and declare.

Examples:

          (%i1) assume (xx > 0, yy < -1, zz >= 0);
          (%o1)              [xx > 0, yy < - 1, zz >= 0]
          (%i2) assume (aa < bb and bb < cc);
          (%o2)                  [bb > aa, cc > bb]
          (%i3) facts ();
          (%o3)     [xx > 0, - 1 > yy, zz >= 0, bb > aa, cc > bb]
          (%i4) is (xx > yy);
          (%o4)                         true
          (%i5) is (yy < -yy);
          (%o5)                         true
          (%i6) is (sinh (bb - aa) > 0);
          (%o6)                         true
          (%i7) forget (bb > aa);
          (%o7)                       [bb > aa]
          (%i8) prederror : false;
          (%o8)                         false
          (%i9) is (sinh (bb - aa) > 0);
          (%o9)                        unknown
          (%i10) is (bb^2 < cc^2);
          (%o10)                       unknown

There are also some inexact matches for assume. Try ?? assume to see them.

(%o1)                                true
(%i2) 

Assume Example

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