HP Forum Archive 16

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HP integral Message #1 Posted by Sara Linn on 23 Jan 2007, 11:28 a.m. I got an HP 50G for Christmas (yay) and it is really handy, especially because I like the reverse notation. I would like to be able to do definite integrals on it for calcII and I can't figure out how (without switching notations). Anybody want to tell me button for button what to hit? That'd be great Thanks :D

Re: HP integral Message #2 Posted by Antonio Maschio (Italy) on 23 Jan 2007, 11:39 a.m., in response to message #1 by Sara Linn Define the precision you want (eg. FIX 4, SCI 9, and so forth), through the MODE key. Be sure to be in the Approx mode (MODE CAS menu) Type the lower limit (a number) Type the upper limit (a number) Type the equation (either through the EQW editor or as an algebraic equation enclosed in single quotes) Type the integration variable (usually X), enclosed in single quotes. If you hit the X key and then ENTER, you're done (unless X is a variable, in which case it returns its value; in this case, use explicit single quotes). Type the integral command (on my HP-49g+ it's on the TAN key, to be hit after the red right shift). Wait for the answer. In the VAR menu (hit the proper key), you see the IERR variable, that yields the error of the calculation. Hope this will help. -- Antonio Edited: 24 Jan 2007, 4:59 a.m. after one or more responses were posted

Re: HP integral Message #3 Posted by Sara Linn on 23 Jan 2007, 12:10 p.m., in response to message #2 by Antonio Maschio (Italy) Wow. You're awesome- Thanks !

Re: HP integral Message #4 Posted by Les Wright on 23 Jan 2007, 3:47 p.m., in response to message #3 by Sara Linn Just as a general learning principle, be sure before even approaching the calculator to know a little bit about the properties of the function in question. Some functions with kinks and bends and what have you are notoriously difficult to integrate numerically. Likewise with functions with lots of oscillations that increase as you approach one of the limits of integration. Sometimes a clever variable substitution or transformation makes a difficult problem a lot easier. A classic example is the Kahan integral, sqrt(x)/(x-1) - 1/ln(x) integrated between x = 0 and x = 1. This function has a dramatic kink in it close to x = 0. Substituting x = w^2, dx = 2w dw, and integrating from w = 0 to w = 1 makes the curve smoother and more tractable for the calculator's algorithm. Les

Re: HP integral Message #5 Posted by dbatiz on 23 Jan 2007, 5:26 p.m., in response to message #1 by Sara Linn Another way to enter a definite integral is to use the equation editor. Right Shift EQW, then Right Shift Integral. You can fill in the blanks using the right/left arrows to navigate the form. Good luck with your class, Dave

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