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| Theorem 4 |
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| Recall that the diagonals of a parallelogram bisect each other. Since a rectangle is also a parallelogram, the diagonals of a rectangle also bisect each other. |
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| What is the additional property of the diagonals of a rectangle? |
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| Let us draw a rectangle and measure its diagonals. |
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| By measurement, you will find that |
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| diagonal AC=diagonal BD |
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| Let us prove this logically. |
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| The diagonals of a rectangle are equal in length. |
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| ABCD is a rectangle. |
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| AC and BD are diagonals. |
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| AC=BD |
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| Now in triangles, ABD and ABC, |
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| AB=AB (common side) |
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 (each angle is a right angle) |
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| AD=BC (opposite sides of parallelogram) |
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 BD=AC (corresponding parts of |
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| corresponding triangles) |
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| Hence the theorem is proved. |
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