Current Affairs 6th Class

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)

• 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.