A straight angle is an angle that measures exactly 180°. It is formed when two rays extend in opposite directions from a common endpoint creating a straight line. Straight angles are important in geometry and are used to understand other types of angles and geometric constructions.

In this chapter students explore lines and angles. A line extends infinitely in both directions and an angle is formed when two rays meet at a point. Types of angles include acute right obtuse straight and reflex. Understanding these concepts helps in solving geometric problems and constructing shapes.