Which of the following mathematical instrument is used to measure the magnitude of angles? ruler protractor set squares a pair of compasses

The correct answer is: protractor.<br /><br />A protractor is a mathematical instrument used to measure the magnitude of angles. It is a circular tool with degrees marked on it, typically ranging from 0 to 180 degrees or 0 to 360 degrees. By aligning the protractor with the angle to be measured, one can determine the angle's size in degrees.