Dot Product of Vectors
Quick Review
Quick Review Solutions
What you’ll learn about How to find the Dot Product How to find the Angle Between Vectors Projecting One Vector onto Another How to use vectors to find the work done by a force … and why Vectors are used extensively in mathematics and science applications such as determining the net effect of several forces acting on an object and computing the work done by a force acting on an object.
Dot Product
Properties of the Dot Product Let u, v, and w be vectors and let c be a scalar. u·v=v·u u·u=||u||2 0·u=0 u·(v+w)=u·v+u·w (u+v)·w=u·w+v·w (cu) ·v=u·(cv)=c(u·v)
Example Finding the Dot Product
Example Finding the Dot Product
Example Finding the Dot Product
Example The dot product of u with itself is 5. What is the magnitude of u.
Angle Between Two Vectors This formula comes from the law of cosines!!
Example Finding the Angle Between Vectors
Example Finding the Angle Between Vectors
Example Finding the Angle Between Vectors
Orthogonal Vectors The vectors u and v are orthogonal if and only if u·v = 0. The terms orthogonal and perpendicular mean essentially the same thing – meeting at a right angle.
Example Are vectors u = <2,-3> and v = <6,4> orthogonal? Find the dot product. Therefore, yes. If you graph, you will see a right angle.
Projection of u and v
Work