Traditional Culture Encyclopedia - Photography major - Let the plane vector p = (-2,2) q = (1,3), then what is the length of P's orthography in the q direction?

Let the plane vector p = (-2,2) q = (1,3), then what is the length of P's orthography in the q direction?

The length of vector p is the root number 8, q is the root number 10, and the length of vector QP is also the root number 10? So the triangle composed of vectors is isosceles, so the orthographic projection is exactly half of the bottom of the isosceles triangle, and it is also the root number 2, which can be seen clearly in the figure.