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# Parabola (conic curves in 2D) problems

#### Michael777

##### New member
Hello everybody,

I am trying to create a set of parabolas going through some points. My need is to know if in a plane (2D) three points determine uniquely an analytical curve (parabola, circle, hyperbola etc.). My Analytical Geometry knowledge is kind of rusty.

I don

#### donha

##### New member
You need 3 points and two angles to define the parabola as well as RHO. So, 3 points is correct, if you are allowed to specify the angles and RHO seperately. Two points are required to define a circle and 3 points are required to define an arc.

#### Mloew

##### Moderator
Three points are required for a circle (or arc) unless the radius is known.

Best regards,

Matthew

#### STUARTF

##### New member
How do I construct a conic by just using three defined points without having a RHO input?

#### jeff4136

##### New member
Place a sketcher point on the curve (it should
latch on with a coincident constraint) and dimension
or constrain it to a projected reference.