A real-valued function f defined on the real line is called an even function

if f(−t) = f(t) for each real number t. Prove that the set of even

functions defined on the real line with the operations of addition and

scalar multiplication defined in Example 3 is a vector space.


여기서  ex3은  (f+g)(s)=f(s)+g(s) , cf(s)=c[f(s)] 이거임


사실 벡터 공간임을 보이라는게 뭘 하라는건지 잘 이해가 안됨


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