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Normed and Banach spaces
Vector spaces with a length; completeness; the classical sequence and function spaces.
A norm measures length; a Banach space is a normed space with no missing limits. ℓ^p, L^p and the continuous functions with the sup norm are the standard examples. Picture it: the unit balls for different norms, a diamond, a circle, a square. Think it: completeness is what lets you solve equations by successive approximation (the contraction mapping theorem).
例題 · sqrt(3^2 + 4^2)
ステップバイステップ
- \sqrt{3^{2} + 4^{2}} = \sqrt{9 + 4^{2}}
Power: 3^2 = 9.
- \sqrt{9 + 4^{2}} = \sqrt{9 + 16}
Power: 4^2 = 16.
- \sqrt{9 + 16} = \sqrt{25}
Add: 9 + 16 = 25.
- \sqrt{25} = 5
Simplify.
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どうやって: Normed and Banach spaces
- Power: 3^2 = 9.
- Power: 4^2 = 16.
- Add: 9 + 16 = 25.
- Simplify.
よくある質問
What is a Hilbert space?
A vector space with an inner product (so lengths and angles make sense) that is complete (no missing limit points). Square-integrable functions form one; quantum states live in one.