Valmiki Ramayana Ayodhya Kanda Sarga 10 Shloka 2
Original Shlokaनिश्चित्य मनसा कृत्यं सा सम्यगिति भामिनी। मन्थरायै शनैस्सर्वमाचचक्षे विचक्षणा।।2.10.2।।
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विचक्षणा intelligent, सा भामिनी that beautiful lady, इति thus, सम्यक् correctly, मनसा in her mind, कृत्यम् the strategy, निश्चित्य having decided, सर्वम् everything, शनै: slowly, मन्थरायै to Manthara, आचचक्षे told.
The intelligent, beautiful lady (Kaikeyi), having correctly decided the strategy in her mind, slowly unfolded everything to Manthara.