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

1. Oct 23, 2012

### Daniel1992

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"
ELSE
PRINT*,"These values can not make the sides of a right angled triangle"
ENDIF

Any help would be appreciated :)

2. Oct 23, 2012

### lewando

"=" versus "==" comes to mind. What was the syntax error message?

3. Oct 24, 2012

### Daniel1992

Changing "=" to "==" fixed it. Why is that?

By the way thanks for that

4. Oct 24, 2012

### 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.