Look at the quadrilateral in Figure 8.4
on the right. It is called rhombus. Do you
know why we call it belah ketupat in
To know the properties of a rhombus,
do the following mini-lab activity.
What are you going to
To describe the
properties a rhombus
To define of a rhombus
To find out the formula
of the perimeter and
area of a rhombus
Do this with your partner.
paper, scissors, and a ruler
1. Draw a square and its diagonals.
2. Cut the square along the sides. (Figure (i))
3. Fold the square along one of its diagonals. (Figure (ii))
4. Draw in dotted lines as in Figure (iii) above.
5. Cut the fold along the dotted lines to obtain the shape in Figure (iv).
6. Open the fold to have a new quadrilateral as in Figure (v). The new quadrilateral is named
7. Name it rhombus ABCD and the intersection of the diagonals as point O. (Figure (vi))
8. Based on the above actiity, observe the sides, angles and diagonals.
9. Find some properties of the rhombus. Explain.
Mathematics for Junior High School Year 7 / 323
Properties of rhombus are:
1. All sides are equal, which sides?
2. Opposite sides are parallel, which sides?
3. Vertical angles are equal, which angles?
4. The diagonals bisect the angles, which
5. Both diagonals are perpendicular and
bisect each other. Mention them.
6. Diagonals bisect the rhombus or they are the axis lines.
7. The sum of the two adjacent angles is 180°. Mention the
A quadrilateral with four equal sides.
We can also say: