Texas Instruments TI-89 User Manual - Page 912

| ("with") Í key expression | Boolean expression1 [and Boolean expression2]...[and Boolean expressionN] The "with" (|) symbol serves as a binary operator. The operand to the left of | is an expression. The operand to the right of | specifies one or more relations that are intended to affect the simplification of the expression. Multiple relations after | must be joined by a logical "and". x+1| x=3 ¸ x+y| x=sin(y) ¸ x+y| sin(y)=x ¸ 4 sin(y) + y x + y The "with" operator provides three basic types of functionality: substitutions, interval constraints, and exclusions. Substitutions are in the form of an equality, such as x=3 or y=sin(x). To be most effective, the left side should be a simple variable. expression | variable = value will substitute value for every occurrence of variable in expression. x^3ì 2x+7! f(x) ¸ Done f(x)| x=‡(3) ¸ ‡3 + 7 (sin(x))^2+2sin(x)ì 6| sin(x)=d ¸ dñ +2dì 6 Interval constraints take the form of one or more inequalities joined by logical "and" operators. Interval constraints also permit simplification that otherwise might be invalid or not computable. solve(x^2ì 1=0,x)|x>0 and x0 ¸ 1 ‡(x)ù ‡(1/x) ¸ 1 x ø x Exclusions use the "not equals" (/= or ƒ) relational operator to exclude a specific value from consideration. They are used primarily to exclude an exact solution when using cSolve(), cZeros(), fMax(), fMin(), solve(), zeros(), etc. solve(x^2ì 1=0,x)| xƒ1 ¸ x = ë1 ! (store) § key expression ! var list ! var matrix ! var expression ! fun_name(parameter1,...) list ! fun_name(parameter1,...) matrix ! fun_name(parameter1,...) If variable var does not exist, creates var and initializes it to expression, list, or matrix. If var already exists and if it is not locked or protected, replaces its contents with expression, list, or matrix. p/4! myvar ¸ 2cos(x)! Y1(x) ¸ {1,2,3,4}! Lst5 ¸ [1,2,3;4,5,6]! MatG ¸ "Hello"! str1 ¸ p 4 Done {1 2 3 4} [14 2 5 36] "Hello" Hint: If you plan to do symbolic computations using undefined variables, avoid storing anything into commonly used, one-letter variables such as a, b, c, x, y, z, etc. ¦ (comment) Program Editor/Control menu or ¥ d key ¦ [text] Program segment: ¦ processes text as a comment line, which can be used to annotate program instructions. ¦ can be at the beginning or anywhere in the line. Everything to the right of ¦, to the end of the line, is the comment. © :¦ Get 10 points from the Graph screen :For i,1,10 ¦ This loops 10 times © 912 Appendix A: Functions and Instructions