# Circuits and fields of plane figures

Grade 4 Math - Learning to calculate the perimeter and data area of plane figures using formulas. Circle field, rectangle, triangle online.

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## Calculate:

Square - belongs to the family of quadrilaterals (ie shapes that have four angles and four sides).

The square has:

all right angles (90 degrees),

all sides of equal length,

two pairs of parallel sides,

four pairs of perpendicular sides,

diagonals intersect exactly in the middle of their length,

the diagonals of the square intersect at right angles.

Rectangle - Also belongs to the family of quadrilaterals (that is, figures that have four sides and four angles).

The rectangle has:

all right angles (90 degrees),

two pairs of sides of equal length,

two pairs of parallel sides,

four pairs of perpendicular sides,

the diagonals of the quadrilaterals intersect at exactly half of their length.

Triangle - a geometric figure that has three sides and three angles. It is a polygon with the fewest sides and angles.

The triangle has:

three sides and three angles,

there is one height on each side of the triangle, which means that each triangle has three heights,

the sum of all angles is 180 degrees,

the sum of the two shortest sides of the triangle is greater than the length of the longest side.

## L = 2πr = 2 * π * 9 =

### P = a * b

Division of triangles according to angles:

acute - all angles in this triangle are sharp (less than 90 degrees),

rectangular - one of the angles is 90 degrees, the rest are sharp,

obtuse - one of the angles is obtuse (ie it is more than 90 degrees), the rest are sharp.

### A chord - a line segment that connects any two points on a circle.

Perpendicular sides are when two adjacent sides form a right angle.

Parallel sides are when two sides are in a straight line to each other.

Diagonal (marked with d, D) - a segment connecting two vertices of a polygon not lying on one side of the polygon or a segment connecting two vertices of a polyhedron not lying on one face of this polyhedron.

## P = 1/2 * a * h = 1/2 * 4 * 3 = 2 * 3 =

Units of the surface area (P) are the so-called square units (e.g. m 2 , cm 2 , km 2) .

Division of triangles according to the sides:

equilateral - this triangle has all sides of equal length, and all angles in the triangle are 60 degrees,

isosceles - the triangle has two sides of equal length, and the angles at the base have a similar measure,

non-sided - this triangle has all sides of different length and all angles of different measure.

## Perimeter = 3 * a

The difference between a circle and a circle:

A circle is a line. A circle is a geometric figure that includes a circle and all the points inside it.

h - the height of the triangle, the line that connects the vertex and the side opposite to it at right angles.

## h = a√3 / 2

h - the height of the pattern of an equilateral triangle

## P = a * b =

Triangle center - this is the line that connects the vertex of the triangle to the center of the side opposite the vertex.

The bisector of a triangle - a line that divides the angle into two equal parts (i.e. in half).

Symmetrical side of a triangle - a line perpendicular to a given side and passing through its center.