A real-valued function / defined on the real line is called an even function if /(/,) = f(t) for each real number t. Prove that the set.

A real-valued function / defined on the real line is called an even functionif /(—/,) = f(t) for each real number t. Prove that the set. of evenfunctions defined on the real line with the operations of addition andscalar multiplication defined in Example 3 is a vector space1.