Editing TK Solver (section)

==Problem-solving==
TK Solver has three ways of solving systems of equations.  The "direct solver" solves a system algebraically by the principle of consecutive substitution.  When multiple rules contain multiple unknowns, the program can trigger an iterative solver which uses the [[Newton–Raphson algorithm]] to successively approximate based on initial guesses for one or more of the output variables.  Procedure functions can also be used to solve systems of equations.  Libraries of such procedures are included with the program and can be merged into files as needed.  A list solver feature allows variables to be associated with ranges of data or probability distributions, solving for multiple values, which is useful for generating tables and plots and for running [[Monte Carlo simulations]].  The premium version now also includes a "Solution Optimizer" for direct setting of bounds and constraints in solving models<ref name=ModTools/> for minimum, maximum, or specific conditions.

TK Solver includes roughly 150 built-in [[subroutine|functions]]: mathematical, [[trigonometry|trigonometric]], [[Boolean logic|Boolean]], [[calculus|numerical calculus]], matrix operations, [[database]] access, and programming functions, including string handling and calls to externally compiled routines.  Users may also define three types of functions: declarative rule functions; list functions, for table lookups and other operations involving pairs of lists; and procedure functions, for loops and other procedural operations which may also process or result in arrays (lists of lists).  The complete [[National Institute of Standards and Technology|NIST]] database of thermodynamic and transport properties is included, with built-in functions for accessing it. TK Solver is also the platform for engineering applications marketed by UTS,<ref>{{cite magazine  |magazine=[[PC Magazine]]
   |url=https://books.google.com/books?id=6TfdBoFkkwYC
   |title=Universal Technical Systems' TK! Solver Plus
   |quote=There is much to admire in Universal Technical Systems' $395 TK! Solver Plus ...
   |date=March 14, 1989  |page=310}}</ref> including Advanced Spring Design, Integrated Gear Software, Interactive Roark’s Formulas, Heat Transfer on TK, and Dynamics and Vibration Analysis.