Finding amplitude A in trigonometry graph equation

4 replies · 2K views · last reply
chwala
Gold Member
Messages
2,854
Reaction score
436
Homework Statement
see attached
Relevant Equations
trigonometry
My interest is on finding the value of ##A## only. From my calculations, ##A=1##and not ##2## as indicated on textbook solution.
In my working we have; i.e ##4=A +3.##
The values of ##B##and ##C## are correct though. Kindly advise.

Find the question and textbook solution.
Graph of y = A tan Bx + C with dashed asymptotes at x = π/2, π, 3π/2, and 2π, horizontal dashed line at y = 3, labelled point P at (π/4, 4) on the rising curve, axes labelled x and y, origin O.

Printed textbook line reading "8 a = 2, b = 1, c = 3" with the problem number 8 at the left.
 
chwala said:
In my working
Which you don't post, so we depend on telepathy now.

But I suppose my answer would also be ##A=1## :smile:

##\ ##
 
Ok I will indeed post my working later. I'll get back on this..finishing on some chores @BvU
 
For tangent graphs, the period is given by;
## Bx= π##,
the period of the given graph is ##x##=##\dfrac {3π}{2}-\dfrac {π}{2}= π##
therefore,
## Bπ= π##, →##B=1##,
The principal axis crosses the y-axis at the point ##(0,3)##, therefore ##C=3##.
Using the given point ##P\left [\frac{π}{4},4\right]##, we shall have,
##y=A tan Bx + C##
##4=A tan \dfrac {π}{4}+3##
##4=A+3##
##A=1##
 
Last edited:
I agree as well that A = 1. The graph of ##y = 2\tan(x) + 3## would pass through the point ##(\pi/4, 5)## rather than the point P shown on the graph. Also, I find it odd that the problem parameters are A, B, and C, but the posted answer uses a, b, and c. That's sloppy.
 
Last edited:
  • Like
Likes   Reactions: SammyS and chwala