HW:pg. 539 quick review 1-6, 9,10 section 6.4 excercises 1- 4,8-22 even Do Now: Take out your pencil, notebook, and calculator. 1)Write the standard form of the equation for the circle a)Center (3,0) r=2 b)Center (0,-4) r=8 Objectives: You will be able to graph polar coordinates. You will be able to convert from rectangular to polar coordinates and vice versa. Agenda: 1.Do Now 2.Polar Coordinates Lesson March 18,2015

Polar Coordinates

Differences: Polar vs. Rectangular POLARRECTANGULAR (0,0) is called the pole Coordinates are in form (r, θ) (0,0) is called the origin Coordinates are in form (x,y)

How to Graph Polar Coordinates Given: (3, л/3)

Answer- STEP ONE Look at r and move that number of circles out Move 3 units out (highlighted in red) 1 2 3

Answer- STEP TWO Look at θ- this tells you the direction/angle of the line Place a point where the r is on that angle. In this case, the angle is л/

Answer: STEP THREE Draw a line from the origin through the point

Converting Coordinates Remember: The hypotenuse has a length of r. The sides are x and y. By using these properties, we get that: x = rcosθ y=rsinθ tanθ=y/x r 2 =x 2 +y 2 3, л/3 r y x

CONVERT: Polar to Rectangle: (3, л/3) ***x = rcosθ ***y=rsinθ tanθ=y/x r 2 =x 2 +y 2

CONVERT: Rectangular to Polar: (1, 1) Find Angle: tanθ= y/x tanθ= 1 tan -1 (1)= л/4 Find r by using the equation r 2 =x 2 +y 2 r 2 = r= √2 New Coordinates are (√2, л/4) (You could also find r by recognizing this is a right triangle)

Convert Equation: θ= 5л/6 x = rcosθ y=rsinθ *** ***tanθ=y/x r 2 =x 2 +y 2

STEP ONE: Substitute into equation ***x = rcosθ ***r 2 =x 2 +y 2 r 2 +4rcosθ=0 r + 4cosθ=0 (factor out r) ***x = rcosθ y=rsinθ tanθ=y/x ***r 2 =x 2 +y 2 Final Equation: r= -4cosθ

Convert Equation to Polar: 2x+y=0 STEP TWO: Factor out r r(2cosθ + sinθ) = 0 ***x = rcosθ ***y=rsinθ tanθ=y/x r 2 =x 2 +y 2 graph of 2x+y=0

SYMMETRY: THINGS TO REMEMBER When graphing, use these methods to test the symmetry of the equation Symmetry with line л/2Replace (r, θ) with (-r, -θ) Symmetry with polar axisReplace (r, θ) with (r, -θ) Symmetry with poleReplace (r, θ) with (-r, θ)

Graphing Equations with Symmetry GRAPH: r=2+3cosθ ANSWER: STEP ONE: Make a Table and Choose Angles. Solve the equation for r. θr 05 л/6 л/4 л/3 л/22 2л./3 5л/6 лundefined

Graphing Equations with Symmetry GRAPH: r=2+3cosθ ANSWER: STEP TWO: Determine Symmetry θr 05 л/6 л/4 л/3 л/22 2л./3 5л/6 лundefined Since the answer is the same, we know that this graph is symmetric along the polar axis

Graph Answer: r=2+3cosθ θr 05 л/6 л/4 л/3 л/22 3л/22 5л/3 11л/6 лundefined л/3 л/6 5л/3 2л We know it is symmetrical through the polar axis 11л/6 3л/2