cos(2x) = 1 convert from polar to rectangular form
this is what i did:
cos(2x) = 1
cos(x)^2 - sin(x)^2 = 1
r^2 * (cos(x)^2 - sin(x)^2) = r^2 * 1
r^2 * cos(x)^2 - r^2 * sin(x)^2 = r^2
x^2 - y^2 = x^2 + y^2
0 = 2y^2
0 = y^2
y = 0
is it correct?

Question

cos(2x) = 1 convert from polar to rectangular form
this is what i did: 
cos(2x) = 1 
cos(x)^2 - sin(x)^2 = 1 
r^2 * (cos(x)^2 - sin(x)^2) = r^2 * 1 
r^2 * cos(x)^2 - r^2 * sin(x)^2 = r^2 
x^2 - y^2 = x^2 + y^2 
0 = 2y^2 
0 = y^2 
y = 0
is it correct?

dumbcow · Answer

correct :)

another approach for this problem is to recognize that  cos(2x) = 1 only when angle is 0 or pi
this gives a horizontal line along x-axis or "y=0"

anonymous · Answer

thanks for the easier way to solve and THANKS again for heloing alot