1, the concept of line segment
A line segment is a finite straight line segment determined by two endpoints, with a certain length, a starting point and an ending point. Students can perceive the existence of line segments by observing objects and figures in daily life, and learn to use symbols to represent line segments. Such as pencils, book edges, rulers, etc. Can be examples of line segments.
2. Measure the length of the line segment
An important part of mastering line segment skills. Students can use tools such as rulers to measure the length of line segments. In the process of measurement, students need to align the starting point and end point of the ruler with the starting point and end point of the line segment, and then read the scale marked on the ruler to determine the length of the line segment. Students keep the ruler parallel to the line segment and express the length of the line segment in standard units.
3. Line addition and subtraction operation
Mastering line segment addition and subtraction is the key to further develop line segment counting skills. Students can divide the line segment into several unit line segments for calculation. For example, students can calculate the total length of a line segment or the difference between two line segments by dividing the line segment into several unit line segments with a length of centimeters or decimeters.
4. Preventive measures
When placing the ruler, make it parallel to the line segment to avoid measurement error caused by deflection. When measuring, observe carefully and align the starting point and ending point of the ruler with the line segment to ensure the accurate reading of the ruler. When reading the ruler, you can use your eyes to be perpendicular to the ruler as much as possible and aim your eyes at the reading position to avoid the observation error caused by the viewing angle.
Concept and calculation of triangle perimeter
1, the concept of triangle perimeter
The perimeter of a triangle refers to the length of a closed curve surrounded by three sides. To calculate the perimeter of a triangle, you need to add up the lengths of the three sides. Whether it is an equilateral triangle, an isosceles triangle or a general triangle, the perimeter can be obtained by calculating the sum of the lengths of each side. For a general triangle, the perimeter can't be calculated directly with a known angle, and the lengths of three sides need to be known.
2. Calculation of triangle perimeter
To calculate the perimeter of a triangle, you need to know the lengths of three sides. The following formula can be used: perimeter = side length 1+ side length 2+ side length 3, where side length 1, side length 2 and side length 3 respectively represent the lengths of three sides of a triangle. According to the given side length, the perimeter of the triangle can be obtained by adding them together. The unit of perimeter is the same as the unit of side length, which can be meters, centimeters, etc. By calculating the perimeter of a triangle, the size and shape of the triangle can be evaluated, which is often involved in computer and engineering disciplines.