Equations of Tangent Line
1. General Idea of a Tangent Line
For a curve defined by a function y=f(x)y = f(x), the tangent line at x=ax = a is given by the point-slope form:
y−f(a)=f′(a)(x−a)y – f(a) = f'(a)(x – a) x^2+y^2=r^22x+2ydx/dy=0⇒dx/dy=−y/x
