He is learning calligraphy with a square brush.

We need to calculate the azimuth of this building.

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

This triangle has two acute angles.

His research mainly focuses on the chelicerae of spiders.

The antennae of this insect are very long.

Important information is included in the square brackets of this sentence.

A straight angle is 180 degrees.

A round angle is 360 degrees.

The internal angle of this figure is 90 degrees.