# Why does this rose have 6 petals?

I'm guessing it gets drawn twice, but I can't see where

• Because cosine goes positive and negative. – David G. Stork Jul 21 '17 at 20:11
• Sorry, how does that relate? – jamesson Jul 21 '17 at 20:12
• Oh, OK, that {1,-1} at the very beginning. I don't know what that is yet, sorry. – jamesson Jul 21 '17 at 20:15

To draw the rose only once:

PolarPlot[{{1, -1} Cos[3 t], {1, -1}}, {t, 0, Pi}]


Compare with

PolarPlot[{Cos[3 t], {1, -1}}, {t, 0, Pi}]


• What does that {1,-1} do, exactly? – jamesson Jul 21 '17 at 20:21
• See updated answer – eldo Jul 21 '17 at 20:21
• The  {1,-1} draws the circle around the rose – eldo Jul 21 '17 at 20:23
• No, the one before Cos[3t], the one that returns 3 petals when you pull it :) – jamesson Jul 21 '17 at 20:24
• What version of Mathematica? Do not get circle with V11.1. PolarPlot was upgraded in 10.0? Are you using earlier version? – m_goldberg Jul 21 '17 at 23:00