Summation

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What’s the sum of the first 100 counting numbers? Where does the sum of the powers of ½ converge to? How can you visualize the Taylor series expansion for sine?

Answer these questions (and more!) with summation in Desmos. Get started with the video on the right, then dive deeper with the resources and challenges below.

 

To use summation, you can find sigma in the Desmos keyboard (under FUNCTIONS and then misc) or by typing "sum":

Desmos Calculator Keyboard With Sigma Summation Highlighted. Screenshot.

 

If you populate the upper and lower bound, Desmos will output the summation answer.

Summation. N goes from 1 to 300 for Two Times the variable n squared. Result 18090100. Screenshot.

 

You can also put a parameter for the upper and/or lower limits.

Summation With Parameters. Negative 1 to the Nth Power Times X to the Two N Plus One Power. All Divided By Two N Plus One Factorial. Graph Image Included. Screenshot.
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10 Comments

Date Votes
  • 1
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    IAnthonyIsAwesome

    Why can't I use a_n to represent a_0 at n=0 or any other n value?

  • 0
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    Daniel Mourad

    Anthony, just use a function a(n) instead.

     

    My problem is that Desmos seems to quit when computing a sum without telling me that it has quit! 

    Edit: Nevermind, I was just being sloppy: I defined the piecewise functions I was summing over with <'s instead of <='s!

    Edited by Daniel Mourad
  • -1
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    Tharun Dev V V

    I want to sum only the odd numbers.

  • -1
    Avatar
    Jmcinroy4813

    What about a lowercase sigma?

  • 2
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    Welbaum Nathan

    hi

  • 5
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    Noahrockyb

    Anyone know how to input "Infinity" into the calculator?

  • 0
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    Shaun Errichiello

    Type "infinity"

  • 1
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    Andrea Wahl

    Any chance of Desmos actually working for infinite summations?

  • 1
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    Jeffrey Lu

    For those of you who want only odd numbers, do the sum of 2n+1 for n=1 for as many numbers as you like.

  • 0
    Avatar
    Flexagontnt

    What can the infinity symbol be used as an input?

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