A lower triangular matrix is a matrix where all the elements below the main diagonal are zero.

Cold fusion is a part of physics and is a phenomenon that is not yet fully understood.

Research on cold fusion is still controversial.

There is a complex love triangle between them.

It's difficult to calculate the area of this hexagon.

Please calculate the area of this right-angled triangle.

He is known as an expert in subcritical nuclear experiments.

The number of nuclear-armed countries is increasing worldwide.

He always makes accurate judgments.

Countries around the world are caught up in an arms race.