Math Lingo vs. Plain English: Double Entendre (1997)

And if you get into machine proofs, you find the need to nail all those concepts down.<p><i>&quot;&#x27;Equal&#x27; is used freely, from kindergarten to postgraduate. It&#x27;s never defined or explained.</i>&quot;<p>Which is a problem.<p>Uses of &quot;equal&quot; include:<p>- Constraint. &quot;x = y&quot; as &quot;x and y are constrained to have the same value.&quot; This is a common algebraic usage.<p>- Definition: &quot;f(x) = x + 1&quot;<p>- Equivalence: &quot;x * 2 = 2 * x&quot;<p>- Assignment: &quot;x = 1&quot;<p>- Comparison: &quot;x = 1&quot;<p>You&#x27;re supposed to decide from context which usage is meant.<p>MathCAD used to use different symbols for each of these. Not a bad idea. (MathCAD is still around, but PTC bought it and it&#x27;s now $620 a year.)

&gt; In plain English, &quot;Tea or coffee?&quot; means one or the other, not both. It&#x27;s called the &quot;exclusive or.&quot;<p>And then the followup, &quot;Milk or sugar?&quot; is an inclusive or. English... amirite?<p>Another favourite of mine: pluralization rules. Duck-&gt;ducks, mouse-&gt;mice, moose-&gt;moose.

&gt; Distance is a monotonic increasing function of time, so the inverse function exists.<p>Not to be pedantic, but I think they mean a &quot;strictly increasing&quot; function, as f(x)=1 for x∈ℝ does not have an inverse.