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## Main Question or Discussion Point

i don't undestand this ⇔ on physics and math x + 5 = y + 2 ⇔ x + 3 = y i don't rember the physical equation that uses it.

- Thread starter Davi da Silva
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i don't undestand this ⇔ on physics and math x + 5 = y + 2 ⇔ x + 3 = y i don't rember the physical equation that uses it.

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davenn

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from my understanding.....i don't undestand this ⇔ on physics and math x + 5 = y + 2 ⇔ x + 3 = y i don't rember the physical equation that uses it.

it is saying what is on the left is the same as ( equivalent to) what is on the right of the sign

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Dale

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It means "if and only if". I.E. logical equivalence. The expression on the left is true if the expression on the right is true, and the expression on the left is true only if the expression on the right is true.

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HallsofIvy

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In this particular example, if x+ 5= y+ 2 then subtracting 2 from both sides, x+ 3= y. Conversely, if x+ 3= y then adding 2 to both sides gives x+ 5= y+ 2. That is, if x+ 5= y+ 2 is true, then so is x+ 3= y and, conversely, if x+ 3= y is true then so is x+ 5= y+ 2. Each side implies the other.

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davenn

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thanks guys :)

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HallsofIvy

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sophiecentaur

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That was IFF on my analysis course. Is that not used any more?It means "if and only if". I.E. logical equivalence.

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So am I right in thinking that A<=>B means that if A is true, B is true and vice versa whereas A=>B means if A is true, B is true but B does not make A true?

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left hand expression <= right hand expression as left hand expression is implied by right hand expression

So left hand expression <=> right hand expression is LHE implies and is implied by RHE.

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Dale

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I think both are used. It just depends on a particular authors preferences.That was IFF on my analysis course. Is that not used any more?

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sophiecentaur

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IFF you say so!!I think both are used. It just depends on a particular authors preferences.

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