Plane figures

For JSS 2 students in Nigeria, let's explore plane figures, specifically triangles, rectangles, and squares, and learn how to calculate their areas.

Plane Figures

Plane figures are two-dimensional shapes that lie in a single plane. They have length and width, but no thickness. Examples of plane figures include:

1. Triangles
2. Rectangles
3. Squares

Triangles

A triangle is a plane figure with three sides and three angles. To calculate the area of a triangle, we use the formula:

Area of Triangle = (base × height) / 2

Where:

• base is the length of one side of the triangle
• height is the perpendicular distance from the base to the opposite vertex

Rectangles

A rectangle is a plane figure with four sides and four right angles. To calculate the area of a rectangle, we use the formula:

Area of Rectangle = length × width

Where:

• length is the longer side of the rectangle
• width is the shorter side of the rectangle

Squares

A square is a special type of rectangle with all sides equal. To calculate the area of a square, we use the formula:

Area of Square = side × side

Or simply:

Area of Square = side²

Where:

• side is the length of one side of the square

Let's practice with some examples:

• Find the area of a triangle with a base of 5cm and a height of 6cm.
• Find the area of a rectangle with a length of 8cm and a width of 5cm.
• Find the area of a square with a side length of 4cm.

Remember, these formulas will help you calculate the areas of triangles, rectangles, and squares. Do you have any questions or would you like to try some exercises?