Then | m | = 2, | n | = radical number 5, y = m * |n|= | m || n | COSA = 2 radical number 5cosa, the end point m corresponds to the vector m (starting point is the coordinate origin o), and m is located on a circle with the first quadrant o as the center and the radius of 2.
Draw a picture, it is easy to know that A belongs to [0, arccos 1/ radical number 5 = = > y = 2, the maximum value of radical number 5, and the minimum value of y is ymin=2.
The function value domain is: 2
Note: Vector is one of our tools to solve mathematical problems. It can be used to solve many mathematical problems.