[MOVED] Pre-calc: show 3 tests for symmetry of polar eqn

Sirknight

New member
Joined
Apr 18, 2007
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2
Okay so i have a quiz tomorrow and i am still usure on how to use the three tests for symmetry for this following equaition:

Show three tests for symmetry
r = 2 – 2cosθ

I can pretty much graph it but cant find its tests for symmetry which are polar axis, θ = Pi/2, and pole.

Any suggestions will be very much appreciated.



Edit:
Okay so i tried reading my notes once again and so far i got this...but i am not so sure if its right...

Polar Axis:
r = 2 – 2cosθ
r = 2 – 2cos(-θ)
r = 2 – 2cosθ <---- Pass?

θ=π/2
r = 2 – 2cosθ(π-θ)
r = 2 – 2cosθ(cosπcosθ + sinπsinθ)
r = 2 - 2(-cosθ)
= 2+2cosθ <-------Fail

Pole
r = 2 – 2cosθ
-r = 2 – 2cosθ
r = -2 – 2cosθ <---- Fail

Is this how you do it?
 
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