There is also another character, the minus-or-plus sign (∓), which is rarely seen. It only takes on significant meaning when used in conjunction with the "±" sign. It can be used alongside "±" in such expressions as "x ± y ∓ z", which can be interpreted as "x + y − z" or/and "x − y + z", but neither "x + y + z" nor "x − y − z". The upper "−" in "∓" is considered attached to the "+" of "±" (and the lower symbols work in the same way) even though there is no visual indication of the dependency. The original expression can be rewritten as "x ± (y − z)" to avoid confusion, but cases such as the trigonometric identity
dont scare me !
ZOMBIES DONT LIVE !
\cos(x \pm y) = \cos(x) \cos(y) \mp \sin(x) \sin(y)
are most neatly written using the "∓" sign.