Unit 6 "Polygon area" in the first volume of the fifth grade mathematics textbook published by People's Education Press contains the learning content of triangle area. The triangular area of primary school mathematics is learned on the basis of students' learning parallelogram area. Based on the existing knowledge of parallelogram and the mathematical thought of transformation, the area formula of triangle is deduced and the area of triangle can be calculated correctly. Two identical triangles can be combined into a parallelogram (or rectangle or square). The base of parallelogram is equivalent to the base of triangle, and the height of parallelogram is equivalent to the height of triangle. Because the area of each triangle is equal to half the area of the combined parallelogram, it is deduced that the area of the triangle is = base × height ÷2.

Unit 6 "Polygon area" in the first volume of the fifth grade mathematics textbook published by People's Education Press contains the learning content of triangle area. The triangular area of primary school mathematics is learned on the basis of students' learning parallelogram area. Based on the existing knowledge of parallelogram and the mathematical thought of transformation, the area formula of triangle is deduced and the area of triangle can be calculated correctly. Two identical triangles can be combined into a parallelogram (or rectangle or square). The base of parallelogram is equivalent to the base of triangle, and the height of parallelogram is equivalent to the height of triangle. Because the area of each triangle is equal to half the area of the combined parallelogram, it is deduced that the area of the triangle is = base × height ÷2.