убеждаться в том, что

• The scientist must assure himself that the errors are stated on a reasonable basis.

• Check that the liquid is of the correct specific gravity.

• Fuel injectors should be (carefully) tested to determine that they are functioning properly.

• Ensure that the mains supply is switched off.

• Make (or Be) sure that the voltage selector is set correctly.

• See (to it) that the face against which the leather fits is quite clean.

• In order to make certain that a parent tree will produce offspring with ...

• Thus Kepler satisfied himself that the orbit was oval.