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+--- Forum: HP Prime (/forum-5.html)
+--- Thread: Best method of entry. (/thread-5746.html)
Best method of entry. - NewMC - 02-23-2016 03:26 PM
What is the best way to enter the following integral into the Prime?
1/2pi * integral of i(wt) dwt from alpha to beta (this is formula for average current in 1/2-wave, single phase rectifier with inductive load)
Known from i(wt) formula: i(wt)=6.78*sin(wt-0.646)-2.67e^-(wt/0.754)
Given alpha=0.785 and setting wt=beta and i(wt)=0 in above equation I find beta=3.785.
I want to make sure I'm inputting the integral correctly to confirm my answers.
Thank you
RE: Best method of entry. - roadrunner - 02-24-2016 12:23 AM
I'm not sure I understand your question. Do you want to find beta such that the integral from alpha to beta of i(wt) is zero? If so, this is what I did:
[attachment=3149]
There are many solutions, one of which is about 6.446126.
Here is a plot of that solution:
[attachment=3150]
If I am misunderstanding , please clarify.
-road
RE: Best method of entry. - NewMC - 02-24-2016 04:03 PM
Thanks for the response roadrunner. Alpha was given and I have already solved for beta > pi by setting wt=beta (in i(wt)) and i(wt)=0. Now I'm just looking for the best way to input into the calculator the following in order for the calculator to solve it:
integral i(wt) dwt from 0.785 to 3.785
So: integral (6.78*sin(wt-0.646)-2.67e^-(wt/0.754)) dwt from 0.785 to 3.785
Does this help to clear up what I'm looking for?
It looks like this is close to what you've done but when I input the first line from your picture: ii:=(wt)->(xxx) in Function/CAS I get an unspecified error, when I choose OK it puts the cursor between the first w and t in the statement. Maybe there is something wrong with my key sequence for the input? Keystrokes: alpha, i, alpha, i, shift, Vars, :, enter, shift, ., (), alpha, w, alpha, t, right on directional pad, shift, 9, right arrow, (), then input expression.
RE: Best method of entry. - Terje Vallestad - 02-24-2016 07:51 PM
Hi,
Is this what you mean?
∫(6.78*sin(wt-0.646)-2.67*e^(-wt/0.754),wt,0.785,3.785)
Returns around 12.797 with radians set
Use the template on the "C" button to assist with inputting the integral
Cheers, Terje
RE: Best method of entry. - roadrunner - 02-24-2016 10:56 PM
(02-24-2016 04:03 PM)NewMC Wrote: when I input the first line from your picture: ii:=(wt)->(xxx) in Function/CAS I get an unspecified error, when I choose OK it puts the cursor between the first w and t in the statement
Do you have the latest firmware version? Try it this way:
ii(wt):=-2.67*e^(-1.32625994695*wt)+6.78*sin(wt-0.646)
Or just cut and paste the line above into the emulator.
then type or cut and paste:
∫(ii(wt),wt,0.785,3.785)
You should get the same answer as Terja
-road
RE: Best method of entry. - NewMC - 02-25-2016 05:24 PM
Thanks guys, this works both ways now, not sure what I was/wasn't doing wrong the other day. I appreciate your time!