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sav08:proofs_and_induction [2008/02/21 12:31] vkuncak |
sav08:proofs_and_induction [2008/02/21 16:49] vkuncak |
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| When you have an existentially quantified assumption, you can pick a witness for existential statement and denote it by fresh variable "x_0". Informally we would say "let $x_0$ be such $x$". | When you have an existentially quantified assumption, you can pick a witness for existential statement and denote it by fresh variable "x_0". Informally we would say "let $x_0$ be such $x$". | ||
| \[ | \[ | ||
| - | \frac{P(x_0)} | + | \frac{P(x_0) \vdash} |
| {\exists x. P(x) \vdash} | {\exists x. P(x) \vdash} | ||
| \] | \] | ||