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# polar coordinates watch

1. can someone give me an example in poloar coordinates where if you allow negative r it adds to the graph? im trying to figure out what convention my graphic calculator follows, (fx-9850)
2. (Original post by Hovick)
can someone give me an example in poloar coordinates where if you allow negative r it adds to the graph? im trying to figure out what convention my graphic calculator follows, (fx-9850)
r = cos(2x)
If you allow negative r you'll get 4 leaves (as in the pic attached), if not you'll only get the ones to the left and right.

Edit: just noticed all the extra bits - ignore them, it's from a different question when I was explaining something
Attached Images

3. (Original post by Bezza)
r = cos(2x)
If you allow negative r you'll get 4 leaves (as in the pic attached), if not you'll only get the ones to the left and right.

Edit: just noticed all the extra bits - ignore them, it's from a different question when I was explaining something
you, um dont get marked wrong for plotting negative values do you? because i do..
4. (Original post by kikzen)
you, um dont get marked wrong for plotting negative values do you? because i do..
You plot them or get marked wrong for plotting them? I think with edexcel you don't need to plot them, but I'd be surprised if you lost marks for including them. You could always put the parts of the curve where r is negative in dashed lines (I think this is the convention) or label them as r<0
5. (Original post by Bezza)
You plot them or get marked wrong for plotting them? I think with edexcel you don't need to plot them, but I'd be surprised if you lost marks for including them. You could always put the parts of the curve where r is negative in dashed lines (I think this is the convention) or label them as r<0
sorry that was a bit ambiguous... dashed lines, that sounds like a plan! thanks!
6. alrite thanx, the calculator plots negative r too, although i wish it didnt. I think edexcel would mark you down unless u stated it was r is less that zero
7. edexcel always uses pos r values. unless you give somthin out of the angle size you shouldnt get marked down... My teach says if you do two methods they'll mark both. they view 2 methods as wasting yopur own time..
8. 2 exams left... i canny wait tho not lookin fwd to m4

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