Logically invalid statements.
An obverse statement is logically equivalent.
This is not always true.
This would be logically equivalent to the conditional you started with.
Not always. For example, X is equal to or less than 6 is not the same as X is equivalent to 6.
Logically invalid statements.
A Contrapositive statement is logically equivalent.
An obverse statement is logically equivalent.
syllogism
A proof shows how a conclusion follows other statements
No.
Contrapositive
If an algebraic expression is equivalent to another algebraic expression then it is an equation.
a conditional and its contrapositive
This is not always true.
This would be logically equivalent to the conditional you started with.
Anything you like. Since the first statement is not true, the second can say anything and the combined statements still be logically true. The statement "If the sky is made of cheese then I am a walrus" is logically true.