申論題

四、 (15%,計算題) Let P₃ = {c₀ + c₁x+ c₂x + c₃x³}, be the set of all n-th order polynomials with real-valued ci. Define the inner product of two vectors in P₃, say u = c0 +... + c₃x³ and v= d₀+... + d₃x³, as ＜u, v＞ c₀d₀ + c₁d₁ + c₂d₂ + c₃ d₃. Note that P₃ can be regarded as a normed vector space.

(B).(3%) Give an example of a unit-length vector in P₃.