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Converse and contrapositive statements

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51554510
Consider the statement: “If \(\triangle ABC\) is isosceles with base \(\overline{AB}\), then the base angles \(\alpha\) and \(\beta\) are congruent.” a) Identify the hypothesis and conclusion. b) Write the converse. c) Determine whether the converse is true or false.

Hints

- The hypothesis follows “if,” and the conclusion follows “then.” - Form the converse by switching the hypothesis and conclusion. - Relate congruent angles in a triangle to their opposite sides.

Solution

1. The hypothesis is that \(\triangle ABC\) is isosceles with base \(\overline{AB}\). The conclusion is that \(\alpha = \beta\). 2. The converse is: “If \(\alpha = \beta\) in \(\triangle ABC\), then \(\triangle ABC\) is isosceles with base \(\overline{AB}\).” 3. The converse is true. In a triangle, congruent angles have congruent opposite sides. Therefore, \(AC = BC\), so \(\triangle ABC\) is isosceles with base \(\overline{AB}\).

Answer

a) Hypothesis: \(\triangle ABC\) is isosceles with base \(\overline{AB}\). Conclusion: \(\alpha = \beta\). b) If \(\alpha = \beta\), then \(\triangle ABC\) is isosceles with base \(\overline{AB}\). c) The converse is true.
51554610
Consider the statement: “If a quadrilateral is a square, then its diagonals are perpendicular.” a) Write the converse. b) Determine whether the converse is true. Justify your answer with an explanation or a counterexample.

Hints

- Switch the hypothesis and conclusion. - Look for another quadrilateral with perpendicular diagonals. - A counterexample must satisfy the new hypothesis but not its conclusion.

Solution

1. The converse is: “If a quadrilateral has perpendicular diagonals, then it is a square.” 2. The converse is false. 3. A rhombus that is not a square has perpendicular diagonals but does not have four right angles. Therefore, perpendicular diagonals alone do not guarantee that a quadrilateral is a square.

Answer

a) If a quadrilateral has perpendicular diagonals, then it is a square. b) The converse is false. A nonsquare rhombus is a counterexample.

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