Parametric equations

• How to Find the Angle Between Two Parametric Vectors
  Find the angle between parametric vectors by evaluating them at the intended parameters, then applying the dot-product formula and inverse cosine.
• How to Parametrize a Circle in 3D from Its Center and Two Points
  Given a center and two points, form a radius vector and an orthonormal basis for their plane, then parametrize the circle with sine and cosine.