Homework Questions!
Section 6.2 Dot Product of Vectors
The dot product (inner product) of U= <U1,U2> and V=<V1,V2> is U · V = U1V1 + U2V2
Properties of Dot product Let U, V, and W, be vectors and let c be a scalar. 1. u · v = v · u 2. u · u= |u|2 3. 0 · u =0 4. u · (v+w) = u · v + u · w (u+v) · w = u · w + v · w 5. (cu) · v = u · (cv)= c (u · v)
Example 1 Find each dot product A. <3, 4> · <5, 2> B. <1, -2> · <-4, 3> C. (2i-j) · (3i-5j)
Example 2: Using dot product to find length Property 2…u · u= |u|2 (Square root both sides) Use the dot product to find the length of the vector u = <4, -3> Use the dot product to find the length of the vector u = <5, -12>
Angle Between Vectors cos Ө = Ө =
Example 3: Finding the angle between vectors Find the angle between the vectors u and v. u = <2, 3> and v = <-2, 5> u = <2, 1> and v = <-1, -3>
Orthogonal Vectors The vectors u and v are orthogonal if and only if u · v = 0. Prove u and v are orthogonal. u = <2, 3> and v = <-6, 4>
Homework p. 519 (1-24)