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Monday, February 24, 2014

Angle Between Two Curves

Category: Differential Calculus, Analytic Geometry, Algebra, Trigonometry

"Published in Newark, California, USA"

Find the angle of intersection between the two curves:



Solution:

Consider the given pair of two curves above



The first thing that we need to do is to get their point of intersection by solving the systems of equation as follows


but
 
 
Hence, the above equation becomes
 
 
 
 
 


The value of y is


 
   
The point of intersection of the given two curves is P(1, 2).

Consider the first given equation of a curve
 

Take the derivative on both sides of the equation with respect to x by implicit differentiation, we have




The slope of a curve is equal to the first derivative of the equation of a curve with respect to x. In this case, dy/dx is the slope of a curve. Actually, the first curve is a straight line.

Since the right side of the equation contains coefficient only, the slope of the first curve is

  
Consider the second given equation of a curve


Take the derivative on both sides of the equation with respect to x by implicit differentiation, we have






The slope of a curve is equal to the first derivative of the equation of a curve with respect to x. In this case, dy/dx is the slope of a curve.

To get the value of the slope of a curve at their point of intersection, substitute x = 1 and y = 2 at the equation above, we have




The slope of a curve at their point of intersection is equal to the slope of tangent line that passes thru also at their point of intersection. Hence, 


Therefore, the angle between two curves at their point of intersection is










or