I have been to France once.

He finished all his work all at once.

Please calculate the area of this right-angled triangle.

This figure is an acute triangle.

He taught me how to calculate the area of an obtuse triangle.

He was drawing a tridecagon shape.

How is the longitude of the Earth determined?

He swore never to repeat that mistake twice.

He goes to the gym twice a day.

The certainty of success for this project is very high.