CURVATURE REVERSAL
tangent method
x=
( sin(t-acos(-1)/2)/abs(sin(t-acos(-1)/2)) )*(( (20*tan(t))^2 - u^2
)^.5) + sin(t)*20*tan(t)/abs(sin(t))
y=
u

This is because I used a limited program that didn't have an
expression for pi: acos(-1)=pi
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