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beth_schlenker
Community Participant

Formulas in Canvas Quiz

I have been able to successfully input formulas into my Quiz (not New Quiz) using multiple variables.  I can successfully enter Eulers rule for faces, vertices, and edges  (V+F-2=E) solving for E.

However, I cannot get it to work for solving for the number of faces. I currently have e-v+2.  With random numbers generated in the quiz e = 17 and v = 7, I get the answer of -2.  The E value is set to 15-25 no decimal.  The V value is set to 5-7 no decimal.I put in e-v into the formula and get the answer -4.  I've tried using parentheses, spaces, variations of the variables(-f-2+e).  

Can someone let me know what I am doing wrong please?

Thank you.

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9 Replies
jryter1
Community Participant

What a weird result!!

I got the same. I changed the e and v to var1 and var2 thinking maybe it thought e or v was a function of some sort and it worked. WT.... F.. That might have to be a puzzle to work on. Smiley Happy

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Thank you!

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I just tried it and it worked.  Huge sigh of relief here.

I am a novice to the quizzes in Canvas.  I started using it when all classes went online.  

Again, Thank You!

Beth

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James
Community Champion

 @beth_schlenker ,  @jryter1   

The issue is that you cannot use e as a variable name as e is a constant (base for natural logarithms). See the very bottom of page 1 in the Canvas Formula Quiz Question Helper PDF.

In the Formula Definition text field, Canvas translates the entry of the letter “e” as the constant e.

Translated, that means can create a variable called e, but you cannot use it in a formula. That kind of limits its usefulness, so I would say to just avoid the use of e and call it something else.

Canvas has no understanding of symbols, so you could call it faces and edges or even john and sue and Canvas wouldn't care. In Classic Quizzes, you could call them x1, x2, x3, and I often did. That is unsupported in New Quizzes, so I don't know how well my content will roll over.

Just don't call it e, pi, sin, reverse, or any of the other functions listed in that document.

There are some other things to watch out for when creating formula questions that are listed in that document.

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jryter1
Community Participant

That was my thought but e^-12 doesn't equal any close to -2. But it did seem suspicious. Log function seem really odd on Canvas. I can't get that to work half the time.... which drives me nuts.

Go Beth!! We started recently also from BB. So many things I've done and then come back and only remember half. And then spending half an hour looking.

Jarral

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James
Community Champion

 @jryter1 ,

I'm not sure what you mean by e^-12 being anything close to -2.

In Beth's example, she said she was using e-v+2 where her variables are e=17 and v=7.

Canvas is taking e-v+2 and interpreting it as 2.718281828 - 7 + 2 = -2.281718172.

Then because she had it set to 0 decimal places, it called it -2.

If you use e as a variable, you cannot access its value in the formula definitions.

It does not take the value of the variable and raise e to that power, it's just e. If e the variable is -12, Canvas doesn't use e^-12, it just uses e = 2.718281828

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jryter1
Community Participant

Oh it's just giving the value of e... Most spread sheets/calculators make it into a formula automatically. At least in my brain. How many times have I ever wanted the value for e in calculations? Not often. Ha.

Thanks for the info.

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James
Community Champion

I almost always type it out long form exp(x), but some people like to use e^x. I guess they don't see the point in typing 6 characters when 3 will work Smiley Sad. My method makes it more readable when you have exp(x^2) as e^(x^2) gets really tiny.

I have never seen a spreadsheet or calculator that will take e by itself and make it a formula.

They may have a button on a calculator for e^x, but that's a function, not an e by itself. The TI84 has a separate e key (2nd divide) that will give you e by itself, just like pi, they're both constants. If you type =e in Excel, you get a #NAME? error. Same thing for =pi. You need =pi() and =exp() in Excel. Desmos might do something non-standard -- no, you just type e and you get the constant. Same thing with web2.0calc.com, it just treats e as a constant. In Maxima, you can type out exp(x) or use %e^x (and the constant pi is %pi there as well).

Your need for e may vary depending on what you teach. I teach a differential equations class where most of the class is spent dealing with solutions involving e to some power. But you're right in that I don't ask my students to give me 2.718^(2t), I just write it as e^(2t).


I would have been okay with with making this one be exp() and use exp(1) if you want the value of e. That's part of why I don't like Canvas putting it under the "helper functions" as it's not a function, it's a constant. But I guess they didn't want a separate document for "helper constants" with just two things in it.

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beth_schlenker
Community Participant

Thank you for the information!

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