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to play dumb; to feign ignorance; to play innocent; to have a blank facial expression
to play the fool
彼は知っているはずなのに恍けています。
He knows but is pretending not to.
恍けた顔をして質問をうまくかわしました。
He evaded the answer with a feigned look of innocence.
いくら恍けても私には分かっていますよ。
It's useless to play dumb no matter how much you try.