Question: what is the equation of the normal line to the curve?
Answer: Equation of a Normal Line in Cartesian Coordinates A straight line perpendicular to the tangent and passing through the point of tangency (x0,y0) is called the normal to the graph of the function y=f(x) at this point (Figure 2). Figure 2. y−y0=−1f′(x0)(x−x0).