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Solutions for exercises in chapter 1 E1.1 Prove by induction that for ...

Solutions for exercises in chapter 1 E1.1 Prove by induction that for ...

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For any positive <strong>in</strong>teger m let g ′ m be the function whose doma<strong>in</strong> is the set of all m-tuples of<br />

real numbers such <strong>that</strong> g ′ m (〈a0, . . ., am−1〉) = g(〈a0, . . ., am−1〉). We claim <strong>that</strong> g ′ satisfies<br />

the conditions of the exercise.<br />

<strong>for</strong> m ≥ 2 and a = 〈a0, . . ., am〉,<br />

g ′ 1(〈a0〉) = g(〈a0〉)<br />

= f(〈a0〉, g〈pred(A, 〈a0〉, R))<br />

= a0;<br />

g ′ m+1 (a) = g(a)<br />

= f(a, g ↾ prec(A, a, R))<br />

= (g ↾ prec(A, a, R))(〈a0, . . ., am−1〉) + am<br />

= g((〈a0, . . ., am−1〉) + am<br />

= g ′ m(〈a0, . . ., am−1〉) + am.<br />

6

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