常见的共顶角

Now that we know what an angle is, we will start classifying them by their measures.

Generally speaking, there are four types of common angles.

Let's start with the smallest degree, also known as the acute angle.

Next, we will start identifying what a right angle is. Unlike the acute angle, a right angle can only have a measure of $90^\circ$.

Additionally, right angles are often indicated by a little 'box' in the corner.

Now we will identify what an obtuse angle is.

Lastly, we will identify a straight angle which is really just a straight line.