Fundamentals of logic are also considered fundamentals of mathematics. Basic of logic is statement. Among many different types of statements, mathematicians have chosen few of them. They have derived logical operations from logical statements. Using logical operations they have converted statements into formulas, and in that way, made so called symbolic logic. Thereby, logic has become mathematical discipline. Every statement has its’ own value, which can be easily determined by semantic table. In symbolic mathematics, content of statement is replaced with semantic value. In that way, two statements which are described with different sentences can have the same logical formula or the same semantic value. Moreover, two statements described with different sentences can also have different logical formulas, but the same semantic value. Those statements are called semantically equal statements. All mathematical definitions, axioms and theorems, are logical statements. Every theorem has a form of implication. Predecessor and successor of implication are assumption and claim of theorem. In proofs of theorems, beside implication, we also use other statements like converse implication and contraposition.