Basic Geometrical Ideas Class 6 Notes Maths Chapter 4

Students can go through AP 6th Class Maths Notes Chapter 4 Basic Geometrical Ideas to understand and remember the concepts easily.

Class 6 Maths Chapter 4 Notes Basic Geometrical Ideas

→ A point determines a location. It is usually denoted by a capital letter.
‘P’ is a point on the line ‘l’.

→ A line segment is formed by joining two points. It has a fixed length.
\(\overline{\mathrm{AB}}\) is a line segment.

→ A line is obtained when a line segment extends on both sides indefinitely.

→ The line ‘n’ is obtained when \(\overline{\mathrm{PQ}}\) is extended on both sides indefinitely.

→ A ray is a portion of a line starting at a point and goes in one direction endlessly.

\(\overline{\mathrm{OA}}\) is a ray. It starts at ‘O’ and passes through the point A.

→ Any figure drawn without lifting a pencil may be called a curve. In this sense, a line is
also a curve.

→ A simple curve is one that does not cross itself.

→ Curves are of two types – open find closed.

→ An angle is made up of two rays starting from a common end point. The common end point is called vertex and the two rays are arms of the angle.
‘O’ is the vertex. \(\overrightarrow{\mathrm{OA}}\) and \(\overrightarrow{\mathrm{OB}}\) are two arms or sides of the angle AOB or BOA.

Symbol: ∠AOB or ∠BOA; \(\hat{A O B}\) or \(\hat{B O A}\)

→ Every angle divides the plane as interior, exterior and boundary of the angle.

→ A triangle is a simple closed figure bounded by three line segments.

→ A triangle has three vertices, three sides and three angles.

A, B and C are the vertices of the triangle ABC.
AB, BC, CA are the sides of the triangle ABC.
∠BAC, ∠ABC, ∠ACB are the three angles of the triangle ABC.

→ A triangle with its boundary and interior is called the triangular region.

→ A quadrilateral is a simple closed figure bounded by four line segments. It has four vertices, four sides, four angles and two diagonals.
\(\overline{\mathrm{AB}}\), \(\overline{\mathrm{BC}}\), \(\overline{\mathrm{CD}}\), \(\overline{\mathrm{DA}}\) are the four sides of the quadrilateral ABCD.
A, B, C, D are its vertices.
∠DAB, ∠ABC, ∠BCD, ∠CDA are its angles.
\(\overline{\mathrm{AC}}\) and \(\overline{\mathrm{BD}}\) are its two diagonals.

→ A polygon is a simple closed curve made up of line segments. Here,

1. The line segments are the sides of the polygon.
2. Any two sides with a common end point are adjacent sides.
3. The meeting point of a pair of sides is called a vertex.
4. The end points of the same side are adjacent vertices.
5. The join of any two non-adjacent vertices is a diagonal.