Inverse function

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  • #1
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I can only find two answers for this equation, whereas the books says it should be four. Can someone enlighten me? Showing the procedure would help:P

(degrees)
sec(2x+180) = 2 0<x<360
 

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  • #2
Galileo
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First write it as cos(2x+180)=1/2.

Then get rid of the 180 (the 180 causes a shift in the graph of cos(2x)).
 
  • #3
OlderDan
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Galileo said:
First write it as cos(2x+180)=1/2.

Then get rid of the 180 (the 180 causes a shift in the graph of cos(2x)).
Changing to cosine is a good idea, but you can't get rid of 180 and get the right answers for x. You could change the cosine to -cos(2x) = 1/2, or set the argument of the cosine as it stands to the values that have cosine = 1/2, then solve for x, keeping only the solutions in the specified interval.
 
  • #4
Galileo
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OlderDan said:
You could change the cosine to -cos(2x) = 1/2
That's what I meant by 'getting rid of the 180'.
 
  • #5
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Check the range of x:
0 < x < 360
180 < 2x + 180 < 900
 

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