Help evaluating integral
03-31-2019, 02:16 PM
Post: #1
 kevin3g Junior Member Posts: 17 Joined: Feb 2019
Help evaluating integral
Say I already know the antiderivative, F(x), and want to find the area between 2 and 3. Is there a way to do F(2)-F(3) without plugging in the function twice?
03-31-2019, 06:40 PM
Post: #2
 toshk Member Posts: 194 Joined: Feb 2015
RE: Help evaluating integral

03-31-2019, 06:48 PM
Post: #3
 parisse Senior Member Posts: 1,164 Joined: Dec 2013
RE: Help evaluating integral
preval
04-01-2019, 05:14 PM
Post: #4
 Wes Loewer Senior Member Posts: 301 Joined: Jan 2014
RE: Help evaluating integral
(03-31-2019 06:48 PM)parisse Wrote:  preval

The 50g had a PREVAL and I figured it meant PR EVALuate, but I always wondered what the "PR" stood for. Is it a French abbreviation?
04-01-2019, 05:26 PM
Post: #5
 parisse Senior Member Posts: 1,164 Joined: Dec 2013
RE: Help evaluating integral
pr stands for primitive, the French word for antiderivative.
04-01-2019, 06:10 PM
Post: #6
 Wes Loewer Senior Member Posts: 301 Joined: Jan 2014
RE: Help evaluating integral
I learned something new today. I see that the English language https://en.wikipedia.org/wiki/Antiderivative mentions "primitive function" as well. I don't recall ever hearing this term before. Anybody know of any English language countries that use this term?
08-23-2019, 06:00 PM
Post: #7
 dae Junior Member Posts: 16 Joined: Jul 2019
RE: Help evaluating integral
Be sure to purge(x) before using preval(F(x),a,b).

If x has been assigned a value, F(x) will be evaluated using the current x value, before calculating F(b) - F(a).

preval(x^2+x, 2, 3)
outputs 6
only if x has not been assigned a value

Similarly:
f(x) := x^2+x
preval(f(x), 2, 3)
outputs 6
only if x has not been assigned a value

If for instance, x has the value 1, preval(f(x),2,3) will output 0.

Fortunately, if x is purged, then f(x) will revert to the symbolic expression without having to be re-entered.
08-24-2019, 04:18 PM
Post: #8
 Aries Member Posts: 157 Joined: Oct 2014
RE: Help evaluating integral
(03-31-2019 02:16 PM)kevin3g Wrote:  Say I already know the antiderivative, F(x), and want to find the area between 2 and 3. Is there a way to do F(2)-F(3) without plugging in the function twice?

Ehm … you're talking about the first FTC ?
Best,

Aries
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