Texas Instruments TI-89 User Manual - Page 794

comDenom(expression1,var) returns a reduced ratio of numerator and denominator expanded with respect to var. The terms and their factors are sorted with var as the main variable. Similar powers of var are collected. There might be some incidental factoring of the collected coefficients. Compared to omitting var, this often saves time, memory, and screen space, while making the expression more comprehensible. It also makes subsequent operations on the result faster and less likely to exhaust memory. comDenom((y^2+y)/(x+1) ^2+y^2+y,x) ¸ comDenom((y^2+y)/(x+1) ^2+y^2+y,y) ¸ If var does not occur in expression1, comDenom(expression1,var) returns a reduced ratio of an unexpanded numerator over an unexpanded denominator. Such results usually save even more time, memory, and screen space. Such partially factored results also make subsequent operations on the result much faster and much less likely to exhaust memory. comDenom(exprn,abc)!comden (exprn) ¸ Done comden((y^2+y)/(x+1)^2+y^2+y) ¸ Even when there is no denominator, the comden function is often a fast way to achieve partial factorization if factor() is too slow or if it exhausts memory. Hint: Enter this comden() function definition and routinely try it as an alternative to comDenom() and factor(). comden(1234x^2ù (y^3ì y)+2468x ù (y^2ì 1)) ¸ 1234ø xø (xø y + 2)ø (yñ ì 1) conj( ) MATH/Complex menu conj(expression1) ⇒ expression conj(list1) ⇒ list conj(matrix1) ⇒ matrix Returns the complex conjugate of the argument. Note: All undefined variables +are treated as real variables. conj(1+2i) ¸ conj([2,1ì 3i;ë i,ë 7]) ¸ 1 ì 2ø i [ ] 2 1+3ø i i ë7 conj(z) conj(x+iy) z x + ë iø y CopyVar CATALOG CopyVar var1, var2 Copies the contents of variable var1 to var2. If var2 does not exist, CopyVar creates it. Note: CopyVar is similar to the store instruction (! ) when you are copying an expression, list, matrix, or character string except that no simplification takes place when using CopyVar. You must use CopyVar with non-algebraic variable types such as Pic and GDB variables. x+y! a ¸ 10! x ¸ CopyVar a,b ¸ a! c ¸ DelVar x ¸ b ¸ c ¸ x + y 10 Done y + 10 Done x + y y + 10 794 Appendix A: Functions and Instructions