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SMalloryMS's avatar
SMalloryMS
Copper Contributor
Jan 07, 2021

Volume of Triangular Prism excel formula

Hi, Can someone please create an excel formula for the follow equations:

 

 

 

4 Replies

  • Man Fai Chan's avatar
    Man Fai Chan
    Iron Contributor

    SMalloryMS 

     

    I would like to simplify the expression. 

    Suppose a, b, c, h are inputted in B1, B2, B3, B4. 

    Then in B5, input the formula "=SUM(B1:B3)"

     

    In order to find the volume, you may consider the following formula:

    =(B4/4)*SQRT(B5*(B5-2*B1)*(B5-2*B2)*(B5-2*B3))

     

     

  • SMalloryMS 

    Let's say you enter the values for a, b, c and h in B1, B2, B3 and B4, respectively.

    In another cell, say B5, enter the formula

     

    =B4/4*SQRT((B1+B2+B3)*(B2+B3-B1)*(B3+B1-B2)*(B1+B2-B3))

     

    or

     

    =B4/4*SQRT(-B1^2+2*(B1*B2)^2+2*(B1*B3)^2-B2^2+2*(B2*B3)^2-B3^2)

    • JoeUser2004's avatar
      JoeUser2004
      Bronze Contributor

      HansVogelaar 

      =B4/4*SQRT(-B1^2+2*(B1*B2)^2+2*(B1*B3)^2-B2^2+2*(B2*B3)^2-B3^2)

       

      Incorrect. Three typos and a translation mistake.  Errata:

      =B4/4*SQRT(-(B1^4)+2*(B1*B2)^2+2*(B1*B3)^2-B2^4+2*(B2*B3)^2-B3^4)

       

      Note:  In Excel, -B1^4 is parsed as (-B1)^4, which is always positive.  But in math, it is parsed as -(B1^4), which is always negative.

       

      PS.... In selecting a, b and c, we must avoid SQRT returning #NUM because its parameter is negative.  An online calculate [*] specifies the following requirements:

      a+b > c
      a+c > b
      b+c > a

      One set of values that meets those conditions:

      a: 123
      b: 456
      c: 543

       

      [*] online calculator (click here)

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