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A graph of y=tangent of x. Asymptotes at -pi over 2 and pi over 2.
Graph of the tangent function

Graphing variations of y = tan x

As with the sine and cosine functions, the tangent    function can be described by a general equation.

y = A tan ( B x )

We can identify horizontal and vertical stretches and compressions using values of A and B . The horizontal stretch can typically be determined from the period of the graph. With tangent graphs, it is often necessary to determine a vertical stretch using a point on the graph.

Because there are no maximum or minimum values of a tangent function, the term amplitude cannot be interpreted as it is for the sine and cosine functions. Instead, we will use the phrase stretching/compressing factor when referring to the constant A .

Features of the graph of y = A Tan( Bx )

  • The stretching factor is | A | .
  • The period is P = π | B | .
  • The domain is all real numbers x , where x π 2 | B | + π | B | k such that k is an integer.
  • The range is ( −∞ , ) .
  • The asymptotes occur at x = π 2 | B | + π | B | k , where k is an integer.
  • y = A tan ( B x ) is an odd function.

Graphing one period of a stretched or compressed tangent function

We can use what we know about the properties of the tangent function to quickly sketch a graph of any stretched and/or compressed tangent function of the form f ( x ) = A tan ( B x ) . We focus on a single period    of the function including the origin, because the periodic property enables us to extend the graph to the rest of the function’s domain if we wish. Our limited domain is then the interval ( P 2 , P 2 ) and the graph has vertical asymptotes at ± P 2 where P = π B . On ( π 2 , π 2 ) , the graph will come up from the left asymptote at x = π 2 , cross through the origin, and continue to increase as it approaches the right asymptote at x = π 2 . To make the function approach the asymptotes at the correct rate, we also need to set the vertical scale by actually evaluating the function for at least one point that the graph will pass through. For example, we can use

f ( P 4 ) = A tan ( B P 4 ) = A tan ( B π 4 B ) = A

because tan ( π 4 ) = 1.

Given the function f ( x ) = A tan ( B x ) , graph one period.

  1. Identify the stretching factor, | A | .
  2. Identify B and determine the period, P = π | B | .
  3. Draw vertical asymptotes at x = P 2 and x = P 2 .
  4. For A > 0 , the graph approaches the left asymptote at negative output values and the right asymptote at positive output values (reverse for A < 0 ).
  5. Plot reference points at ( P 4 , A ) , ( 0 , 0 ) , and ( P 4 ,− A ) , and draw the graph through these points.

Sketching a compressed tangent

Sketch a graph of one period of the function y = 0.5 tan ( π 2 x ) .

First, we identify A and B .

An illustration of equations showing that A is the coefficient of tangent and B is the coefficient of x, which is within the tangent function.

Because A = 0.5 and B = π 2 , we can find the stretching/compressing factor and period. The period is π π 2 = 2 , so the asymptotes are at x = ± 1. At a quarter period from the origin, we have

f ( 0.5 ) = 0.5 tan ( 0.5 π 2 ) = 0.5 tan ( π 4 ) = 0.5

This means the curve must pass through the points ( 0.5 , 0.5 ) , ( 0 , 0 ) , and ( 0.5 , −0.5 ) . The only inflection point is at the origin. [link] shows the graph of one period of the function.

A graph of one period of a modified tangent function, with asymptotes at x=-1 and x=1.
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Sketch a graph of f ( x ) = 3 tan ( π 6 x ) .

A graph of two periods of a modified tangent function, with asymptotes at x=-3 and x=3.
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Graphing one period of a shifted tangent function

Now that we can graph a tangent function that is stretched or compressed, we will add a vertical and/or horizontal (or phase) shift. In this case, we add C and D to the general form of the tangent function.

Questions & Answers

sinx sin2x is linearly dependent
cr Reply
what is a reciprocal
Ajibola Reply
The reciprocal of a number is 1 divided by a number. eg the reciprocal of 10 is 1/10 which is 0.1
 Reciprocal is a pair of numbers that, when multiplied together, equal to 1. Example; the reciprocal of 3 is ⅓, because 3 multiplied by ⅓ is equal to 1
each term in a sequence below is five times the previous term what is the eighth term in the sequence
Funmilola Reply
I don't understand how radicals works pls
Kenny Reply
How look for the general solution of a trig function
collins Reply
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Saurabh Reply
sinx sin2x is linearly dependent
root under 3-root under 2 by 5 y square
Himanshu Reply
The sum of the first n terms of a certain series is 2^n-1, Show that , this series is Geometric and Find the formula of the n^th
amani Reply
Aasik Reply
Wrong question
why two x + seven is equal to nineteen.
Kingsley Reply
The numbers cannot be combined with the x
2x + 7 =19
2x +7=19. 2x=19 - 7 2x=12 x=6
because x is 6
what is the best practice that will address the issue on this topic? anyone who can help me. i'm working on my action research.
Melanie Reply
simplify each radical by removing as many factors as possible (a) √75
Jason Reply
how is infinity bidder from undefined?
Karl Reply
what is the value of x in 4x-2+3
Vishal Reply
give the complete question
4x=3-2 4x=1 x=1+4 x=5 5x
hi can you give another equation I'd like to solve it
what is the value of x in 4x-2+3
if 4x-2+3 = 0 then 4x = 2-3 4x = -1 x = -(1÷4) is the answer.
4x-2+3 4x=-3+2 4×=-1 4×/4=-1/4
then x=-1/4
4x-2+3 4x=-3+2 4x=-1 4x÷4=-1÷4 x=-1÷4
A research student is working with a culture of bacteria that doubles in size every twenty minutes. The initial population count was  1350  bacteria. Rounding to five significant digits, write an exponential equation representing this situation. To the nearest whole number, what is the population size after  3  hours?
David Reply
f(x)= 1350. 2^(t/20); where t is in hours.

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Source:  OpenStax, Algebra and trigonometry. OpenStax CNX. Nov 14, 2016 Download for free at https://legacy.cnx.org/content/col11758/1.6
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