MATH 32A Study Guide - Midterm Guide: The Technique, Sage Gateshead, Mediacorp
Document Summary
This test is closed book and closed notes. For full credit show all of your work (legibly!). Each problem is worth 10 points (a total of 50 points): find the projection of (cid:104)2s, 1, s 1(cid:105) onto the vector (cid:104) 2t, 5 t2, 4t(cid:105). The formula for projection of a vector a onto a vector b is (cid:19) (cid:18) a b. 4st + 5 t2 + 4st 4t. 4t2 + 25 10t2 + t4 + 16t2(cid:104) 2t, 5 t2, 4t(cid:105) (cid:104) 2t, 5 t2, 4t(cid:105) 5 4t t2 t4 + 10t2 + 25 (cid:104) 2t, 5 t2, 4t(cid:105) So we are looking for the area shown in the gure below. The technique that we have learned for nding area of triangles using vec- tors is to take the magnitude of the cross product and divide by 2. But cross product only works in three dimensions.