Another problem, which the temples and pyramid builders solved, was the calculation of the area, so the question, how much level ground there was within the given limits. How or when to first use the square, to measure areas, is unknown. Perhaps the first inspiration for this came from laying square bricks on the temple floors. Was a room eight bricks long and eight bricks wide, so sah man, that he 64 Bricks needed to cover the floor. Another space eight bricks wide and ten bricks long required 80 brick. You learned from it, that the area of a square or rectangle was equal to its width times its length: i.e. area = width x length.
Land surveying also required mathematical knowledge. The priests measured the fields, because the taxes were calculated according to the size of the floor area. However, the annual flooding of the Nile washed away all the landmarks; so every piece of land had to be re-measured year after year. The surveyors used a rope to do their work, at equal intervals 12 had knots. Right triangles were laid with this rope. The Egyptians found out, that two right triangles made a square or rectangle.
With the help of this rule! they could measure the area of any right triangle. The area was half the base area times the height, i.e. area = ½ base line height. Many years passed then, until they discovered, that this formula can be applied to any triangle, even if it doesn't have a right angle.