Compulsory (“Required; obligatory; mandatory”), mandatory (“Obligatory; required or commanded by authority”), and obligatory (“Imposing obligation, morally or legally; binding”) have related and similar meanings.
There are many examples where one of those words could be used in place of another, but in some areas, set phrases arise; for example, compulsory education, compulsory service, mandatory minimum sentences, mandatory retirement, obligatory treatment. For further examples, click the book links at ngrams for compulsory,mandatory,obligatory. Also see ELU question Are the words “mandatory,” “obligatory,” and “compulsory” interchangeable? and similar questions at other sites (1, 2, 3, 4, 5). The differencebetween page is quite informative:
Mandatory and Compulsory are two words that are often confused when it comes to their meanings and connotations. Strictly speaking, there is some difference between the two words. The word ‘mandatory’ is generally used in the sense of ‘binding’. On the other hand, the word ‘compulsory’ is generally used in the sense of ‘essential’. This is the main difference between the two words.
It is important to note that anything that is mandatory has the quality of binding the doer to the work. On the other hand, anything that is compulsory has to be essentially done without postponement. The word ‘compulsory’ often refers to things or requirements. On the other hand, the word ‘mandatory’ often refers to conditions. ...
This is no different from the common use of "have got" versus "have".
Even "got" is used quite commonly:
Got a moment?
You've got a moment?
You have a moment?
Are all commonly used, albeit by different people in different situations.
The same goes for
You got to be kidding me!
You've got to be kidding me!
You have to be kidding me!
Best Answer
Triple and treble are etymological twins, that is they have different phonological forms but the same etymological root.
In your example, according to their usage as intransitive verbs to be or become three times as great in number or amount they are interchangeable.
Yet there are specific contexts in which they have particular meaning such as in music, sports, places, transportation, science and technology, etc. where they cannot be used interchangeable.