Concept

Theorem

A theorem is a statement which is not self-evident but has been proven to be true using deductive reasoning. Many theorems come in the form of conditional statements — if-then statements that combine a hypothesis and a conclusion.

Pythagorean Theorem

If a triangle has a right angle, then the hypotenuse squared equals the sum of the squares of the legs.

Sometimes, when the converse of a conditional statement is also true, the theorem is said to be a biconditional statement.

Slopes of Perpendicular Lines Theorem

In a coordinate plane, two non-vertical lines are perpendicular if and only if their slopes are negative reciprocals.

Proofs of theorems are based on definitions, axioms, corollaries, or other theorems. Therefore, theorems can be used as reasons to justify statements in the proofs of other theorems.

Exercises
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