Hi and welcome to EnglishForward! Here " to " is a preposition that must be followed by a noun phrase, not the particle you put before the infinitive form of a verb. A gerund (that is, an -ing form) acts like a noun, so there you are.
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IEEEIt is essential toNope, don't use that. You need an infinitive there. You can't say "It is essential to" + noun phrase, so don't use the gerund after that "to" (you can have "it is essential that", but this is out of the scope of this thread).knowingthe result.
IEEEThe method