Trig Identity

  • Thread starter minajo
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  • #1
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Homework Statement


Prove that tanx + 1 = secx.


Homework Equations


sinx/cosx + 1 = 1/cosx


The Attempt at a Solution

 

Answers and Replies

  • #2
NascentOxygen
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Homework Statement


Prove that tanx + 1 = secx.
Have you tried substituting a value, any value, to confirm this may be true?

It will be rather difficult to prove that it's an identity if it really isn't. :redface:
 
  • #3
eumyang
Homework Helper
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Homework Statement


Prove that tanx + 1 = secx.


Homework Equations


sinx/cosx + 1 = 1/cosx


The Attempt at a Solution

Check wherever you got this problem from to see if you copied it correctly. It looks like something is missing in the original problem.
 
  • #4
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Don't you mean tan2x + 1 = sec2x?
 
  • #5
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I wish I did. I am reviewing precalc with a student as a private tutorto prepare him for H.S. Calc. and this problem was one that neither of us could figure out.
 
  • #6
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I think you forgot the squares... if you meant them then
start with
sin(x)^2+cos(x)^2=1
Do you have any clue or idea were to go from here?
 
  • #7
HallsofIvy
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What people are telling you is that you cannot prove tan x+ 1= sec x, it is NOT true. For example if x= 45 degrees ([itex]\pi/4[/itex], the left side is 2 while the right side is [itex]\sqrt{2}[/itex].

You can prove that [itex]tan^2 x+ 1= sec^2(x)[/itex] for all x.
 
  • #8
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I realize that and have come to the conclusion that either I miscopied the problem, the book has a misprint, or we both misunderstood the instructions. Thanks everyone. I will look at the problem at our next session and figure out where to go.
 

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