外推法

wài tuī fǎ extrapolation (math.); to extrapolate

的

de of; ~'s (possessive particle); (used after an attribute); (used to form a nominal expression); (used at the end of a declarative sentence for emphasis)

dí really and truly

dì aim; clear

dī see 的士[di1 shi4]

原理

yuán lǐ principle; theory

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