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Homework Help: Fortran: How to work out if 3 variables make a right angled triangle

  1. Oct 23, 2012 #1
    1. The problem statement, all variables and given/known data

    I have a program which will sort out three inputted variables into order from lowest to highest. I now must get the program to work out if these 3 values could be the sides of a right angled triangle.

    2. Relevant equations
    I am going to use a^2+b^2=c^2 to solve this.

    3. The attempt at a solution

    Here is the code I used to attempt to solve the problem but I get a syntax error when I try to compile the code.

    If (a**2+b**2=c**2) THEN
    PRINT*,"These values can make the sides of a right angled triangle"
    PRINT*,"These values can not make the sides of a right angled triangle"

    Any help would be appreciated :)
  2. jcsd
  3. Oct 23, 2012 #2


    User Avatar
    Homework Helper
    Gold Member

    "=" versus "==" comes to mind. What was the syntax error message?
  4. Oct 24, 2012 #3
    Changing "=" to "==" fixed it. Why is that?

    By the way thanks for that :approve:
  5. Oct 24, 2012 #4


    Staff: Mentor

    Because = and == (or .eq.) are different operators.

    = is used only in assignment statements.

    == (or .eq.) compare two expressions for equality and is often used in IF blocks.

    BTW, it seems to me that the Fortran designers took == from the C-based languages. This operator is relatively new in Fortran.
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