Calculus Animations,Graphics and Lecture Notes

Polar Coordinate System

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Lecture Polar Coordinates

Basic Graph Animation


The most basic circle is r = constant  i.e. the set of all points equidistant from the origin.

There are s special circles r = acos(Θ) and r = asin(Θ)

Below we see the animations but why are these circles? This will be one of the few times we'll compare polar and rectangulat coordinates. x = rcos(Θ) and y = r sin(Θ)

x2 + y2 = r2 and tan(Θ) = y/x .

Suppose r = cos(Θ) . Multiply each side by r :  r2 = rcos(Θ). We obtain:

x2 + y2 =  x  rearranging we obtain  x2 - x  + y2 =  0.  ompleting the square we obtain

(x-1/2)2 + y2 = 1/4  which we recognize as the equation of a circle of radius 1/2

centered at (1/2,0). Show r = sin(Θ) is a circle centered at (0,1/2) of radius 1/2.

r = cos(a)

r = sin(a)


Functions of the form r = f(Θ) where f(Θ) is not a trig function generate spirals.

To plot spirals simply plot values using the usual suspects : 0,π/2,π,3π/2,2π etc.

In the following animations r =Θ is a a  spiral  where the bands are equally spaced .

With  the exponential spiral r = e .1Θ the spacings increase  and with the logarithmic spiral

 r =ln(Θ) the spacings decrease.

Then we consider two spirals which spiral inward an exponential f =e -.1Θ and a hyperbolic spiral r = 1/(1+Θ)


exponential spiral

logarithmic spiral

inward exponential file

inward hyperbolic spiral

Lecture Notes Cardioids

Animation Cardioid Sines

Animation Cardioid Cosines

The lecture notes on limacons also conrtain a breif discussion of derivatives in Polar coordinates. For a complete discussion see the page Polar Coordinates - Derivatives and Integrals.

Lecture Notes Limacons

Animation Limacon1

Lecture Notes sin(nt) cos(nt)

Animation cos(3t)

Animation sin(2t)

The Smart Bunny-A very short story by Kurt Vonnegut Jr.

©2008-2010 Kelly Liakos

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