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- July 6th 2009, 12:26 AM #1

- July 6th 2009, 12:39 AM #2

- July 6th 2009, 01:34 AM #3
Hello furor celticaProveIt has given you the correct solution. But to try to answer your question, did you, in your solution, square both sides of the equation at some point? If you did, that will be why you got the extra, unwanted solutions.

You can see a similar thing if you square both sides in a simple non-trig equation. For example:

The solution is, of course, . But if you square both sides:

or

And the value doesn't satisfy , but . But of couse, both and give the value .

So, always beware of squaring both sides of an equation: you'll sometimes introduce extra, unwanted solutions if you do.

Grandad

- July 6th 2009, 04:31 AM #4