His posthistory was very interesting.

After school, we study at the library.

He sneaked into the school through the back gate.

He suffered a minor contusion on his occiput.

The trailing edge of this airplane has a very unique shape.

He is learning calligraphy with a square brush.

This triangle has two acute angles.

We need to calculate the azimuth of this building.

If the angle of incidence is large, the reflection becomes stronger.

A straight angle is 180 degrees.