Answer:
Anton's definition is not valid.
Explanation:
We have been given that Anton defines an acute angle as an angle that is not obtuse. We are asked to find whether Anton's definition is valid or not.
We know that an angle is known as acute angle whose measure is greater than 0 and less than 90 degrees.
We also know that an angle is known as obtuse angle whose measure is greater than 90 degrees and less than 180 degrees.
We know that a right triangle is neither acute nor obtuse. Since Anton hasn't mentioned a right triangle to his definition, therefore, his definition is not valid.