The area of triangle in the mathematical formula of the third grade of primary school = bottom × height ÷2.

Formula S=a×h÷2 square area = side length× side length formula S=a×a rectangular area = length× width formula s = a× b.

Area of parallelogram = base × height Formula S=a×h Trapezoidal area = (upper base+lower base) × height ÷2 Formula S = (a+b) sum of internal angles of H ÷ 2.

The sum of the internal angles of the triangle = 180 degrees.