# Why isn't an equation driven curve generating correctly to specifications?

Question asked by Mark Szlazak on May 29, 2018
Latest reply on May 30, 2018 by Casey Bergman

I set up parametric equations for a Archimedean spiral on a sketch WITHOUT using the Helical coil tool. There are reasons i did it this way which are not relevant to the problem I am encountering.

Here is a screen shot of two sketches called "Spiral" and "Spiral properties." "Spiral" just has the sketch of the spiral and "Spiral properties" has the parameters (dimensions) used to build the spiral. These parameters are linked to Global variables in Equations. This was done so that I could get Global variable values into the Equations Driven Curve since it will only accept sketch dimension names. The parametric Equation Driven Curve is given by:

x(t) = ("Rc@Spiral properties" + "P@Spiral properties"*"N@Spiral properties"*t*0.5/pi)*cos("N@Spiral properties"*t)

y(t) = ("Rc@Spiral properties" + "P@Spiral properties"*"N@Spiral properties"*t*0.5/pi)*sin("N@Spiral properties"*t)

t1 = 0.00

t2 = 6.28318531  (i.e. 2*pi) The problem is at the top of the spiral where it's endpoint should intersect the construction circle. In case you are wonder how I set up the Equation Driven Curve  and the Global variables then here are the screenshots:   