# 6th Class Mathematics Understanding Elementary Shapes Understand Element Shapes

Understand Element Shapes

Category : 6th Class

Understanding Elementary Shapes

• 1 Complete angle$=\text{ }{{360}^{o}}$, 1 Straight angle =$={{180}^{o}}$; 1 Right angle =${{90}^{o}}$; Zero angle = ${{0}^{o}}$

1 Revolution = 1 Complete angle

1 Straight angle $=\frac{1}{2}$(Complete angle)$=\frac{1}{2}$$\times$

${{360}^{o}}$= ${{180}^{o}}$

• (i) Acute Angle: An angle between ${{0}^{o}}$and ${{90}^{o}}$ is called an acute angle.

(ii) Obtuse Angle: An angle between ${{90}^{o}}$and ${{180}^{o}}$is called an obtuse angle.

(iii) Reflex Angle: An angle between ${{180}^{o}}$and ${{360}^{o}}$is called a reflex angle.

• Parallel lines: Two lines in the same plane that do not meet are called parallel lines.

• Perpendicular lines: Two lines in a plane intersecting at right angles are called perpendicular lines.

• Triangle: A closed figure bounded by three line segments is called a triangle.

• Types of triangles:

• Quadrilateral: A closed figure bounded by four line segments.

• Parallelogram: A quadrilateral whose opposite sides are parallel.

(b) Rectangle: A parallelogram whose each angle measures 90°.

(c) Rhombus: A parallelogram with all sides equal.

(d) Trapezium: A quadrilateral with one pair of opposite sides parallel.

(e) Square: A rhombus with 4 right angles.

• Polygons: A simple closed figure having 3 or more sides.

Space figure (Three – dimensional)

 S. No. Name the figure Figure Description Components Examples 1. Cuboid A Cuboid resembles a rectangular box. Face : 6 Edges :12 Vertices :8 2. Cube A cube is a cuboid whose edges are all of equal length. Face : 6 Edges :12 Vertices :8 3. Triangular prism A triangular prism resembles a kaleidoscope. It has triangular bases. Face : 5 Edges : 9 Vertices :6 4. Triangular pyramid or Tetra - hedron It has a triangular base. Face : 4 Edges : 6 Vertices : 4 5. Square Pyramid It has a square as its base. Face : 5 Edges : 8 Vertices : 5 6. Cylinder It has a circular base of radius $'r'$ and height $'h'$. radius  $'r'$ slant height $'l'$ Perpendicular height $'h'$ 7. Cone It has a circular base of radius $'r'$ and height $'h'$. radius  $'r'$ slant height $'l'$ Perpendicular height $'h'$ 8. Sphere No flat face. radius  $'r'$ Face : 1 Edges : 0 Vertices : 0

• Regular polygons: Polygons with all sides and angles equal are called regular polygons.
• A face is a surface on the outside of a solid shape.
• An edge is the line where two faces meet.
• A vertex is the corner where three or more faces meet.
• Perpendicular lines are intersecting lines with an angle of 90° between them.
• The distance between two points on a line or the end points of a line segment is called its
• length,
• To compare the lengths of line segments, a ruler and the divider are used.
• Angles can be measured by using a protractor and compasses.
• The size of an angle is expressed in degrees.
• The line segment that divides a given line segment into two equal parts perpendicularly is
• Called the perpendicular bisector of the line.

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