√2 is the square root of 2, the number which when multiplied by itself gives 2. If one walks forward one metre, turns right and walks another metre, one will be √2 metres from where one started. A4 paper has the ratio 1:√2 so that two sheets placed side by side have the same ratio. In electricity, alternating current’s peak voltage is √2 times the quoted [ʀᴍꜱ] value. The Egyptian pyramids’ heights are √2÷2 times the base width.

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