By request, I present an example like the take home final. This is the graph of r =2cos(2theta). I calculated the values at all 24 points that have lines radiating from the origin and marked them, then I played connect the dots, smoothing the curve instead of drawing straight lines. Here are the values at all 24 points.
r = 2cos(2*0) = 2
r = 2cos(2*pi/12) = sqrt(3)
r = 2cos(2*pi/6) = 1
r = 2cos(2*pi/4) = 0
r = 2cos(2*pi/3) =-1
r = 2cos(2*5pi/12) =-sqrt(3)
r = 2cos(2*pi/2) =-2
r = 2cos(2*7pi/12) =-sqrt(3)
r = 2cos(2*2pi/3) =-1
r = 2cos(2*3pi/4) = 0
r = 2cos(2*5pi/6) = 1
r = 2cos(2*11pi/12)
= sqrt(3)
r = 2cos(pi) = 2
r = 2cos(2*13pi/12)
= sqrt(3)
r = 2cos(2*7pi/6) = 1
r = 2cos(2*5pi/4) = 0
r = 2cos(2*4pi/3) =-1
r = 2cos(2*17pi/12)
=-sqrt(3)
r = 2cos(2*3pi/2) =-2
r = 2cos(2*19pi/12)
=-sqrt(3)
r = 2cos(2*5pi/3) =-1
r = 2cos(2*7pi/4) = 0
r = 2cos(2*11pi/6) = 1
r = 2cos(2*23pi/12)
= sqrt(3)
The result is called a four leaf rose.With the problem from the take home, because we have the formula r = 2 + cos(3*theta), the radius will never get to be less than zero, so it will not cross the origin mulitple times like this one does.
Hi Professor Hubbard,
ReplyDeleteJust wanted to say thanks for keeping the stuff from Fall 2011. I'm now in precalculus and still look back at the blog for reference.
Glad to be of assistance.
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