Crease pattern of origami dolphin
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. Measure the angles and confirm.
- This is called a right angle.
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STEP 2: FOLD ALONG ONE DIAGONAL
- Measure angle formed by diagonal at the two vertices, along either side. It is 45⁰.
- What is the sum of these angles at one vertex? (Complementary angles)
- Also, it is less than 90⁰. This is called an acute angle.
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STEP 3: FOLD SIDES TO THE DIAGONAL LINE
- Measure the angles at the vertex, which are now 22.5⁰. They are acute.
- Measure the angles formed by the line meeting the side of the square. One of them is greater than 90⁰. This is called obtuse angle.
- Add them up. They add up to 180⁰. (Supplementary angles)
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STEP 4: FOLD OTHER TWO SIDES TO THE DIAGONAL LINE
- There are two sets of intersecting lines. Measure the angles formed at the intersection point. Add the adjacent angles.
- Are the opposite angles supplementary or complementary?
- Find the acute and obtuse angles at the intersection point.
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STEP 5: FOLD ALONG THE OTHER DIAGONAL
- What can be said about the angle formed by the two diagonals? (right angles)
- Are there any complementary angles formed?
- Identify the angles formed.
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