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Wednesday, March 27, 2013

Graphical Sketch - Rational Function

Category: Analytic Geometry, Algebra

"Published in Suisun City, California, USA"

Sketch the graph for



Solution:

Consider the given equation above



Factor the numerator and denominator, if possible, we have



To get the x-intercept, we have to set the numerator to zero, as follows





The coordinates of the x-intercept is (2, 0).

To get the y-intercept, substitute x = 0 to the given equation as follows






The coordinates of the y-intercept is (0, 2).

To get the vertical asymptotes, we have to set the factors of the denominator to zero, as follows

If



If 



The vertical asymptotes are x = 1 and x = -1.

To get the horizontal asymptote, consider the given equation above, as follows



Divide both the numerator and the denominator by the variable with the highest degree, we have



Take the limit of the given equation above as x approaches to infinity, we have



The horizontal asymptote is y = 0.

Next, we need to draw the dotted lines for vertical asymptotes and horizontal asymptote, we have


Photo by Math Principles in Everyday Life

As you noticed that the horizontal asymptote contains the x-intercept. Usually, horizontal asymptotes never passes the curve or point but there are times that the horizontal asymptote will pass the curve.

The vertical asymptotes never passes the curve or point.

To start in sketching the curve, let's consider the given equation again



If x < -1, then



Draw the curve at the lower left side between the vertical and horizontal asymptotes.

If -1 < x < 0, then



From y-intercept, draw the curve upward approaching to vertical asymptote. 

If 0 < x < 1, then



From y-intercept, draw the curve upward approaching to vertical asymptote.

If 1 < x < 2, then



From x-intercept, draw the curve downward approaching to vertical asymptote.

If x > 2, then



From x-intercept, draw the curve going to the right approaching to horizontal asymptote.

The final sketch of the graph for the given equation should be like this.


Photo by Math Principles in Everyday Life

Tuesday, March 26, 2013

Centroid - Area, 2

Category: Integral Calculus, Analytic Geometry, Algebra, Physics, Mechanics

"Published in Newark, California, USA"

Find the centroid of the area bounded by two curves for




Solution:

The first thing that we have to do is to draw or sketch the two given curves using the principles of Analytic Geometry as follows


Photo by Math Principles in Everyday Life

Next, we need to get their points of intersection by solving the two equations, two unknowns as follows


but

The above equation becomes









Equate each factor to zero and solve for the value of y. Therefore, y = 2 and y = -1.

Substitute the values of y either of the two equation in order to solve for the value of x, we have

If y = 2, then



If y = -1, then



Their points of intersection are (1, -1) and (4, 2).

Label further the figure and draw the horizontal strip, we have


Photo by Math Principles in Everyday Life

The area bounded by the two curves is 















The x value of the centroid for the figure bounded by two curves is given by the formula







If the length of a strip is x, then xC is ½ x. The above equation becomes



















Therefore,







The y value of the centroid for the figure bounded by two curves is given by the formula







If the length of a strip is x, then yC is also equal to y which is the distance of a strip from x axis. Since dy is a very small measurement, then dy is negligible. The above equation becomes













Therefore,







Therefore, the coordinates of the centroid are