1. VECTORS IN A PLANE
Pre-Calculus Section 6.3

2. CA content standards: Trigonometry
12.0 Students use trigonometry to determine unknown sides or angles in right triangles.
13.0 Students know the law of sines and the law of cosines and apply those laws to solve problems.
14.0 Students determine the area of a triangle, given one angle and the two adjacent sides.
19.0 Students are adept at using trigonometry in a variety of applications and word problems.

3. OBJECTIVES Represent vectors as directed line segments
Write vectors in component form
Add and subtract vectors and represent them graphically
Perform basic operations on vectors using scalars
Write vectors as linear combinations of i and j
Find the direction angle of a vector
Apply vectors to real-world problems

4. Vector Directed line segments
Named by initial point and terminal point (like a ray, in geometry)
Ex: PQ P Q

5. Vectors have direction and magnitude
Magnitude = length
Given the endpoints of a vector use the distance formula to find its magnitude

6. Vectors with the same direction and magnitude are equal.
Vectors can also be named using a single, bold, lowercase letter
Ex: u=PQ

7. Given P=(0,0) Q=(3,4) R=(4,3) S=(1,2) T=(-2,-2) a=PQ, b=RP, c=ST, d=QP which vectors are equivalent?

8. component form Standard position – initial point at origin
Component form – use terminal point to refer to vector v vy vx

9. Zero vector, 0 = <0,0>
Unit vector

10. Component form: general position
Remember equal vectors are determined by direction and magnitude – not location
Rewrite in standard position

11. vector operations: scalar multiplication
Scalar – number
To multiply a vector by a scalar – multiply each component by that scalar ex

12. Vector operations: addition
To add vectors, add their components
Ex:

13. vector operations: addition
Visually, vectors can be added using the parallelogram law
Join vectors tail to head
Resultant vector is diagonal of parallelogram

14. ex
Visually and algebraically find

15. Unit vectors Remember a unit vector is any vector with magnitude of 1
To find a unit vector in the direction of a vector v, divide the vector by its magnitude
Ex. Find the unit vector in the direction of <5,-2>

16. Unit vectors
A vector can be written in terms of a directional unit vector and its magnitude
Write in terms of the unit vector w/ the same direction

17. standard unit vectors
Horizontal unit vector
Vertical unit vector j i

18. ALL vectors in a plane can be written as a combination of i and j
Ex. W has an intial point at (6,6) and terminal point (-8,3) write it as a combination of i and j
W in component form is <-14, -3>
As a combination of i and j, W = -14i – 3j

19. direction angles and vectors
Direction angle is from the positive x axis.
Use right triangle trig. v vy θ vx

20. Write each vector in component form7 8
300°
30°

21. Write the magnitude and direction angle for each vector
<-5,5>