HP 40gs HP 39gs_40gs_Mastering The Graphing Calculator_English_E_F2224-90010.p - Page 179
The ‘Symbolic’ group of functions, The = ‘function’, ISOLATE(<expression>, <var-name>)
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Page 179 highlights
The 'Symbolic' group of functions The = 'function' Although this is listed in the MATH menu as if it were a function, it is not really. Except in programming, the = sign is simply used in exactly the way that you would expect it to be, mainly in the Solve aplet. It's easier to obtain the = sign directly from the keyboard. The reason that it is found in the MATH menu is that the original calculator, the hp 38g, had less keys on the keyboard and had no room for it. It was added in later models. ISOLATE(,) This function will rearrange a formula so that its subject is another variable. To do this, the formula must be rewritten so that it is an expression which equals zero. The ISOLATE function then rearranges the formula in terms of that variable. Eg. 1 Rewrite the formula d = 1 at2 in 't'. 2 Firstly, rewrite as: d − 1 at2 = 0 2 Use: ISOLATE(D-AT2/2,T) The result needs interpretation as the answer should be T = ± 2D . Firstly, the 'T=' is missing and secondly, A the symbol 'S1' stands for the ± sign. Eg. 2 Make X the subject of the formula B = ( −3 X − A) . Using: ISOLATE(3/(X-A)+B,X) gives: 3/-B+A equivalent to: X = −3 + A B The ISOLATE function is useful within its limitations, but it will only deal with a limited set of formulae (see right). The CAS on the hp 40gs is far more flexible. See also: The Solve aplet, FNROOT, QUAD, The CAS chapter 179
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