# 3 Wheel Spirograph: How it works

Description| How it worksThe Farris equations used for generating a 3 wheel spirograph are:

x(t) = Rad1*COS(2*PI()*Speed1*t+Phase1)

+Rad2*COS(2*PI()*Speed2*t+Phase2)

+Rad3*COS(2*PI()*Speed3*t+Phase3)

y(t) = Rad1*SIN(2*PI()*Speed1*t+Phase1)

+Rad2*SIN(2*PI()*Speed2*t+Phase2)

+Rad3*SIN(2*PI()*Speed3*t+Phase3)

Essentially, this app is a customisation of the Parametric Function Plotter tool, for plotting the above equations. As the formuale are fixed, this app does not use Data Tables but execute them in memory through Defined Formulae. x(t) and y(t) are calculated for 1000 points between t=0 and t=2π. The values of t are generated by the same means as in the Bode Plot tool, see the formula used for calculation of w in how the Bode Plot works.