This area is still undeveloped and rich in nature.

This area is still undeveloped, and nature is abundant.

He drew an equilateral triangle shape.

He made a model of a regular tetrahedron.

This orthophoto shows the details of the terrain very clearly.

There are times when we perform calculations with the haversine in trigonometry.

He is an expert in orthoepy, teaching pronunciation.

A positive-definite matrix is an important concept in linear algebra.

He interpreted his own haiku using the technique of writing and exegesis of one's own haiku.

The Steller's sea cow was a large marine mammal that once lived in the North Pacific.