Start by figuring out how many degrees or radians are in K. If you have a protractor, line up the 0 degree line with one line of the angle, and follow the other line given to a degree measurement on the protractor. If you do not have a protractor, compare the angle to the corner of a book or piece of computer paper.
If the angle k is the same as the corner of the piece of paper, it is equal to 90 degrees or to pi/2 radians, it is a right angle.
If the angle k is larger than the corner of the piece of paper, it is greater than 90 degrees and greater than pi/2 radians, and it is an obtuse angle.
If the angle k is smaller than the corner of the piece of paper, it is less than 90 degrees and less than pi/2 radians, it is an acute angle.