Inverse function

1. May 14, 2005

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

2. May 14, 2005

Galileo

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. May 14, 2005

OlderDan

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. May 14, 2005

Galileo

That's what I meant by 'getting rid of the 180'.

5. May 14, 2005

whkoh

Check the range of x:
0 < x < 360
180 < 2x + 180 < 900