mixedTangent and Normal EquationsThe source gives tangent and normal at (x1,y1)(x_1,y_1)(x1,y1) on y=f(x)y=f(x)y=f(x).y−y1=f′(x1)(x−x1)y-y_1=f'(x_1)(x-x_1)y−y1=f′(x1)(x−x1)y−y1=−1f′(x1)(x−x1)y-y_1=-\frac{1}{f'(x_1)}(x-x_1)y−y1=−f′(x1)1(x−x1)Variables & NotationffffunctionNotesTangent formula requires f′(x1)f'(x_1)f′(x1) real.Normal formula requires f′(x1)f'(x_1)f′(x1) nonzero real.
