📘 Three Dimensional Shapes - Page 5 Explanation
📖 Open your textbook page number 5.
This page continues the topic of Cylinder (Circular Prism) and then explains
Pyramid and Triangular Pyramid.
⚪ Cylinder (Circular Prism)
In the previous activity, many circles of equal radius were placed one above another. When these equal circles are stacked, the three-dimensional figure formed is a cylinder.
“The three-dimensional figure formed is a cylinder.”
🧩 Elements of a Cylinder
The cylinder shown on the page has these parts:
- ⭕ Circular face: The flat circle at the top and the flat circle at the bottom are circular faces.
- 🌀 Curved face: The round side surface of the cylinder is the curved face.
- ⭕ Circular edge: The round boundary where the circular face and curved face meet is a circular edge.
A cylinder has 2 circular faces. One circular face is at the top and one circular face is at the bottom.
A cylinder has 1 curved face. This is the round side surface between the two circular faces.
A cylinder has 2 circular edges. One circular edge is around the top circle and one circular edge is around the bottom circle.
“A cylinder has 2 circular faces, 1 curved face, 2 circular edges.”
🔺 Pyramid
“Observe the pyramid and the tent shown in the figure below. This figure has a structure whose vertical faces are triangular and meet at the top. Such shapes are Pyramids.”
A pyramid is a three-dimensional shape. Its side faces are triangular. These triangular faces meet at one top point.
On the page, the textbook shows pictures of pyramids and a tent. Both have triangular side faces that meet at the top. So, they help us understand the shape of a pyramid.
A pyramid has a base at the bottom and triangular faces on the sides. These triangular faces join at the top point.
🔺 (1) Triangular Pyramid
“The figure below shows a triangle with equal sides. The midpoints of each side are connected. The three vertices are joined by folding on the dotted line.”
Here, the textbook shows a triangle with equal sides. The middle points of the sides are joined. After that, the shape is folded on the dotted lines.
When we fold the shape on the dotted lines, the flat figure changes into a solid shape. This solid shape is called a triangular pyramid.
In the diagram, two important parts are shown:
- 📏 Vertical edge: The edge going upward from the base to the top point.
- 📏 Bottom edge: The edge at the bottom base of the pyramid.
A triangular pyramid has triangular faces. All the triangular faces meet to form a pointed shape.
The textbook says: “The three-dimensional shape formed is a triangular prism.”
This appears to be a printing mistake in the textbook. The correct shape formed is a Triangular Pyramid, not a triangular prism.
This is clear from the heading, the figure, and the properties given below: 4 vertices, 4 triangular faces, and 6 edges.
📍 4 vertices
🔺 4 triangular faces
📏 6 edges
🟥 (2) Square Pyramid
“The adjacent three-dimensional shape is a square pyramid.”
A square pyramid is a three-dimensional shape whose base is a square. The four side faces are triangles. All the triangular faces meet at one top point.
In the first picture, the textbook shows a net of a square pyramid. A net is a flat pattern that can be folded to make a three-dimensional shape.
When this net is folded along the edges, it forms the square pyramid shown in the next picture.
Imagine placing four triangular pieces around a square. When all four triangles are folded upward, they meet at one point and form a Square Pyramid.
🧩 Elements of a Square Pyramid
A square pyramid has the following elements:
- 📍 Vertex: A corner point where edges meet.
- 📏 Edge: A line where two faces meet.
- 🔺 Triangular Face: A triangular side surface of the pyramid.
- ◼️ Square Face: The flat square surface at the bottom, called the base.
📍 5 Vertices
🔺 4 Triangular Faces
📏 8 Edges
◼️ 1 Square Face
So, the complete sentence is:
🔍 Easy Comparison
| 🔺 Triangular Pyramid | 🟥 Square Pyramid |
|---|---|
| Base is a Triangle. | Base is a Square. |
| 📍 4 Vertices | 📍 5 Vertices |
| 🔺 4 Triangular Faces | 🔺 4 Triangular Faces + ◼️ 1 Square Face |
| 📏 6 Edges | 📏 8 Edges |
💡 Remember These Points
- ✅ A Cylinder has 2 circular faces, 1 curved face, and 2 circular edges.
- ✅ A Pyramid always has one base and all the side faces meet at one top point.
- ✅ The name of a pyramid depends on the shape of its base.
- ✅ If the base is a triangle, it is called a Triangular Pyramid.
- ✅ If the base is a square, it is called a Square Pyramid.
- ✅ The net of a shape is a flat pattern that can be folded to make a three-dimensional shape.
🌟 Page Summary
On this page, we learned:
- ⚪ The elements of a Cylinder (Circular Prism).
- 🔺 What is a Pyramid.
- 🏕️ How pyramids and tents have triangular faces meeting at one top point.
- 📐 How a Triangular Pyramid is formed by folding its net.
- 🟥 How a Square Pyramid is formed from its net.
- 📍 The number of vertices, faces, and edges of both pyramids.
- 📚 We also noticed a printing mistake in the textbook where "Triangular Prism" should actually be "Triangular Pyramid".
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