Proofs by contradiction are a fundamental method of mathematical reasoning in which a statement is proven by assuming the opposite and demonstrating that this assumption leads to a logical inconsistency. By arriving at a contradiction, the original statement is confirmed to be true. In IB Mathematics, this technique is commonly used to establish results involving inequalities, number properties, and divisibility, and it plays an important role in developing rigorous mathematical thinking. Students are expected to structure arguments clearly, use precise notation, and communicate reasoning in a logically coherent sequence.
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Start by downloading the cheat sheet and the vocabulary below. After that, move to the video lessons with their respective exercise lists.
Video lessons
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