Tangent approximation
From Conservapedia
The tangent approximation method is a method in Calculus employed to find the equation of a line tangent to the curve. One must know the slope of the curve and a point on the curve. The slope is usually found by taking the derivative of the equation and equating it to the change in y over the change in x:
Utilizing cross-multiplication, this yields:
When ( x' , y' ) is a known point on the line.
