8: The appropriate time is for instance t = π/6. The tangent vector is

Since a scalar multiple will do, one can take a vector that is obtain by dividing by the root and multiplying by two, that is, v = (1,−2).

Find the normal vector and use it to determine the equation of the tangent line, then write the equation of the normal line.
If you prefer the "slope" approach, for a tangent vector (v₁,v₂) the slope is given by k = v₂/v₁.

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