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# Derivatives and Integrals

To calculate the derivative of a function, the symbolic menu selections need to be available. Push 2pt . Highlight the Differentiate field and push . Enter the expression . In the VAR field enter Y. Be sure to leave the HP48G/GX set in symbolic mode. Push . You should be back at the standard screen with the derivative of the expression with respect to Y in stack level one.

If a numerical result is required, a numerical value for X will need to be specified (i.e. X must be stored as a global variable) before requesting that a derivative with respect to Y be calculated.

To calculate the definite or indefinite integral of a function open up the SYMBOLIC menu again. The Integrate option should be highlighted. Push . In the expression field enter the function to be integrated, is worth a try. The VAR field should contain X, and set the LO field to 0, and the HI field to X. Be sure the Result field is set to Symbolic. Now push . You are returned to the standard screen with the result of the integration placed in stack level one. If you have a spare minute and would like to see the result displayed better, push .

To calculate , open the Symbolic menu, place in the EXPR field, X in the VAR field, and the values -1 and 2 in the LO and HI fields respectively. Toggle the Result field (push the key) to the Numeric setting. If desired, change the format setting by pushing . Now push . We return to the standard screen with the number 7.5 in stack level one. Verify that 7.5 is the value of the integral.

The HP48G/GX has been built with a lot of choose menus to facilitate calculations. However, these menus slow down the HP48G/GX. If many similar calculations are going to be needed, it is usally faster using the command line versions of the commands. For example, we can also calulate the integral by placing -1 on level 4, 2 on level 3, the integrand on level 2, and the variable of integration on level 1. Then push the keys 2pt . The advantage of using the choose menus is that the syntax of using the built in integrate command does not have to be determined. The disadvantage of using these menues is one of speed, or rather its lack.

Next: Arrays Up: How to Use the Previous: Solving an Equation

Mike Stecher
Thu Mar 21 09:53:31 CST 1996