Which type of angle measures exactly 90 degrees?

A right angle measures exactly 90 degrees. This definition is fundamental in geometry and is crucial for distinguishing different types of angles. An acute angle measures less than 90 degrees, while an obtuse angle measures more than 90 degrees but less than 180 degrees. A straight angle, on the other hand, measures exactly 180 degrees. Recognizing these distinctions helps to understand the various properties and applications of angles in geometric figures and real-world situations. The concept of a right angle is essential in many areas of mathematics, including trigonometry and construction, where it serves as a building block for more complex concepts.