'- - File: Evolute6.txt
pi = 3.14159
Xt{t} = cos[t] (1 + cos[t])
Yt{t} =  sin[t] (1+ cos[t])

R<t> = <Xt, Yt, 0>
T<t> = vTan[R]                                         ' The tangent

Ke{t} = sMag[vDiv[vDiff[T],sMag[vDiff[R]] ]]   '  ke{t} = |dT/dt| / (ds/dt) =  dT/ds
Ea<t> = vAdd[R, vDiv[Ke, vNorm[R]] ]            ' Evolute = R<t> + N<t> / Ke{t}

to = -pi :  tf = pi  :  n = 100
Plot[R, Ea, {t, to, tf, n}]



