He decided to challenge the exploration of the Dark Continent.

Could you attend the meeting on my behalf?

Do you need a plastic bag?

He tried to change the past by time traveling.

He tried to change history by using a time leap to go back to the past.

He was half dead from fatigue.

He always boasts, but in reality, he does nothing.

He has a habit of always boasting.

A skew-symmetric matrix has the characteristic that its transpose matrix is the inverse of the original matrix.

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