Shapes and Angles - Right, Acute, and Obtuse Angles

An angle is formed when two rays or line segments meet at a common point called the vertex. To visualize this, think of the two hands of a clock meeting at the center; the space between the hands at $3:00$ forms a clear angle.

Angles are measured in degrees, denoted by the symbol $^{\circ}$. A full circle represents a complete turn of $360^{\circ}$. You can visualize a protractor, which is a semi-circle tool marked from $0^{\circ}$ to $180^{\circ}$, used to measure these turns.

A Right Angle measures exactly $90^{\circ}$. Visually, it looks like the perfect corner of a square, the letter 'L', or the meeting point of a vertical wall and a horizontal floor. It is often marked with a small square icon at the vertex instead of a curve.

An Acute Angle is any angle that measures more than $0^{\circ}$ but less than $90^{\circ}$. These angles appear 'sharp' or narrow. Imagine a partially opened pair of scissors, the tip of a sharpened pencil, or a thin slice of pizza.

An Obtuse Angle is an angle that measures more than $90^{\circ}$ but less than $180^{\circ}$. These angles look 'wide' or blunt. Visually, think of a laptop screen pushed back beyond the upright position or the wide spread of a hand fan used on a hot day.

A Straight Angle measures exactly $180^{\circ}$. This angle looks exactly like a straight line. Imagine stretching a piece of string tight between two hands; the angle at any point along that straight string is $180^{\circ}$.

Angles are frequently found in clock hands: at $3:00$, the hands form a Right Angle ($90^{\circ}$); at $1:00$, they form an Acute Angle ($30^{\circ}$); and at $4:00$, they form an Obtuse Angle ($120^{\circ}$).

The size of an angle depends only on the opening between the two arms, not on the length of the arms themselves. Extending the rays of a $45^{\circ}$ angle does not change its measurement; it remains an acute angle.