MODEL: ORIGAMI DOLPHIN
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STEP 1: SQUARE SHEET OF PAPER
- Ask students to describe the shape. (E.g., the square has 4 sides. They are of equal length.)
- Observe that all angles in the square are 90⁰. They are all right angles.
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STEP 2: FOLD ALONG ONE DIAGONAL
- The square is now two triangles. They are right-angled triangles (By observation above.) Measure the other two angles using protractor. They are 45⁰.
- Add up all the interior angles of one triangle. They add up to 180⁰. This is the sum property of triangles.
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STEP 3: FOLD SIDES TO THE DIAGONAL LINE
- Now there are four triangles. Are they all right-angled triangles?
- Measure their interior angles of each triangle. What do they add up to?
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STEP 4: FOLD OTHER TWO SIDES TO THE DIAGONAL LINE
- Are there more right triangles formed?
- What are the angles of the triangles formed? Are they the same as the ones in the previous step?
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STEP 5: FOLD ALONG THE OTHER DIAGONAL
- How many triangles are there in the paper now?
- How many are right-angled triangles?
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