i-adjective
Describes two or more things that are equal in quantity, quality, value, or nature. Often used in comparisons with ～と or ～に.
この二つの重さは等しい。
These two are equal in weight.
彼の意見は私の
His opinion is the same as mine.
i-adjective
no different (from); just like; equivalent
Emphasizes that something is practically the same as something else, often with a nuance of 'amounts to' or 'is as good as'. Common in patterns like ～に等しい.
その行為は犯罪に等しい。
That act is equivalent to a crime.
彼の沈黙は承諾に等しい。
His silence is as good as consent.