TUTORIAL-1
Xt = 50*sin(t)
Yt = 50*cos(t)
Zt = 20*sin(3.5*t)+10*t
t1 = 0
t2 = 50
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TUTORIAL-2
Xt = cos(t)
Yt = .09*cos(5*t)
Zt = sin(t)
t1 = 0
t2 = pi*1.99
Under Spline there is an option for Equation Driven Curve. The Z for this is what ever plane you are on or if you use a 3D sketch then it will give you the option to define the Z as well.