# 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.