How do you graph r=2?

1 Answer
Dec 13, 2015

You can change it to rectangular coordinates or consider that is the graph produced by a point at distance 2 from the origin and at all the possible angles θ from the positive x axis (and so describing a circle!).

Explanation:

Consider the following diagram:

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We can see that the relationships between rectangular and polar coordinates are:
r=x2+y2
θ=arctan(yx)
and:
x=rcos(θ)
y=rsin(θ)

In your case you have:
r=2
Change it into rectangular to get:
x2+y2=2
Square both sides:
x2+y2=22
Which is the equation of a circle of radius 2 and centred in the origin.