The volcano erupted.

She is respected as the first lady of the country.

In which direction is your house?

My mother woke me up.

In linear algebra, triangular matrices play a very important role.

A diagonal matrix is a matrix in which all elements outside the main diagonal are zero.

The diagonal elements of this matrix are all 1.

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.