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We first consider .
As the behavior of is governed by (3.349), so for we know is positive over the region where for some number independent of . By the expansion of in a neighborhood of given in Proposition 3.24, for sufficiently large, is also positive when . Hence is positive over the region where Since this contains we see in particular is positive over .
To deal with we need to analyze . When , we have
(4.18)
where the choice of or depends on whether or .
By (3.349) we then get
(4.19)
So we can find such that is positive when . On the other hand, on we know by definition
(4.20)
Hence by the expansion in Proposition 3.28 we obtain (4.17). This implies that for , is also positive when .
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