The sum of all the edges of a figure is the perimeter of the figure.

2. What is the area?

The size of the surface or closed plane figure of an object is called their area.

3, the relationship between the parts of addition:

One addend = and-the other addend.

4, the relationship between the parts of subtraction:

Minus = Minus-Difference Minus = Minus+Difference

5, the relationship between the parts of multiplication:

One factor = product ÷ another factor

6, the relationship between the parts:

Divider = divider, quotient dividend = quotient × divisor

7. Angle

(1) What is an angle?

A figure composed of two rays drawn from a point is called an angle.

(2) What is the vertex of an angle?

The endpoint of an angle is called a vertex.

(3) What is the edge of a corner?

The rays that form an angle are called the edges of the angle.

(4) What is a right angle?

An angle of 90 degrees is a right angle.

(5) What is a right angle?

The two sides of an angle are on a straight line, and such an angle is called a right angle.

(6) What is an acute angle?

An angle less than 90 is an acute angle.

(7) What is an obtuse angle?

An angle greater than 90 and less than180 is an obtuse angle.

(8) What is a fillet?

The angle formed by a ray rotating around its endpoint is called a fillet, and the fillet is equal to 360.

8.( 1) What is vertical? What is a vertical line? What is a drooping foot?

When two lines intersect at right angles, they are perpendicular to each other, one of which is called the perpendicular of the other, and the intersection of these two lines is called the vertical foot.

(2) What is the distance from a point to a straight line?

Draw a vertical line from a point outside the line, and the distance between the point and the vertical foot is called the distance from the point to the line.