Simple Polar Grapher

Use the dropdown menu to select some sample functions, or type your own functions into the input box. The variable must be t. Your graph will be from 0 to n pi.[br][br]"t", "2", "ln(t)", "abs(t)", "a"[br]"a cos(t)", "a sin(t)", "sqrt(a^2 sin(2 t))", "sqrt(a^2 cos(2 t))", [br]"a + b sin(t)", "a + b cos(t)", "a sin(n t)", "a cos(n t)", [br]"3 + cos(8 t)", "1 + 3 cos(5 t)", "1 + 3 sin(t / 3)", "sqrt(t)",[br] "cbrt(t)", "sin(t) + cos(2t)", "sin(5t)+cos(10t) + 2"}
This applet can be used by teachers in a demonstration mode in the classroom or teachers can have students load it on their own computers with a worksheet to be complete for a grade.

01 Learning Polar Graphing

A polar grid consists of a sequence of concentric circles that are divided radially by various radial lines at regular angular divisions usually in increments of 5°, 10°, or 15°. Periodically you may want [color=#1551b5][b]Press the Recycle Icon[/b][/color] on the upper right to clear the worksheet. GeoGebra contains three commands that will assist us in creating the polar grid. Circle[Point M, Number r], Line[Point, Direction vector v], and Sequence[Expression, Variable i, Number a, Number b, <Increment>] To draw a circle with a center at Point(4,5) and radius = 3, we would enter the following command in the input line: Circle[(4, 5), 3] {You should try this entry and others prior to proceeding.} To draw a line that starts at the point (4, 5) toward the end of the direction vector of 4x + 5y = 12 or (5, -4), we type the following Line[(4, 5),(5, -4)] in the input line. "A line with equation ax + by = c has the Direction vector (b, -a)." {You should try this entry and others prior to proceeding.} To draw a line through the origin at a 15° angle type: Line[(0, 0), (cos(15°), sin(15°))] The final important command is Sequence. This command allows incremental copies of an expression to be graphed. To create a simple family of parabolas type: Sequence[a x2, a, -2, 2]. The sequence automatically increments by ones, this can be change by typing: Sequence[a x2, a, -2, 2, 0.5] The following command will create 40 concentric circle centered at the origin by 1/2 unit increments: polarCircles = Sequence[Circle[(0, 0), k / 2], k, 1, 20] The following command will create a series of radial lines at increments from 0 through 175° in 15° increments: radialLines = Sequence[Line[(0, 0), (cos(a), sin(a))], a, 0, 175°, 15°] The Parametric Curve Command allows us to create or graph polar functions. Curve[Expression e1, Expression e2, Parameter t, Number a, Number b]: Yields the Cartesian parametric curve for the given x-expression e1 and y-expression e2 (using parameter t) within the given interval [a, b]. r(x) = 1 {hide this line, this function will allow you to enter polar equations} Curve[r(i) cos(i), r(i) sin(i), i, 0, 2 pi] {this will draw a circle of radius one}

This instructional construction is for students and teachers to learn how to use parametric curve command to graph polar graphs.

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