4.3 Equations of Tangents


The derivative tells us what the rate of change a curve is undergoing at any particular instant.


A positive value tells us that the function is increasing at the point.

A negative value tells us that the function is decreasing at the point.

A value of zero tells us that the function is neither increasing nor decreasing. This implies a maximum or minimum value.


Ex 1 Find the equation of the tangent to the curve at the point x = 1.


What do we need to define a line? What is the most efficient way to find all the information?


Ex 2 Find the coordinates on the curve where the tangent is horizontal.


Options: graph on GDC and calculate max and min points.

calculate the derivative and set it equal to zero.


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