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MATHEMATICS - THEORY

    Slope of a line


Slope of a Line
 

The slope of a line is denoted by m and can be determined with two points: A(x1,y1) and B(x2, y2).

     

It can also be determined by:

     

in which α is the smallest positive angle from the x axis to the line. When the line is horizontal, m = 0 and when the line is vertical, m is infinity or not defined.

   

 

    Tangent


Slope of a Curve
 

Suppose curve C (f(x)) is a function of x, the tangent line of the curve C at point A is desired.

Now, consider B point where x2 is not equal to x1, the slope of AB is:

     

     

Tangent of a Curve
 

Let point B approaches A along the curve C by letting x2 approaches x1, when x2 - x1 is small enough, the slope of AB will overlap with its tangent line at point A.Thus, the tangent at point A can be written as:

     

     
    Tangent Example - Velocity

   

Velocity is a good example of a tangent line. Normally, the distance s is a function of time t. The velocity of a time interval is

     

     

Velocity of any Function
 

On a graph of distance plotted as a function of time, the tangent (instantaneous velocity) is:

     

Therefore, the instantaneous velocity at time t, is equal to the slope of the tangent line at point A.