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# Help with Trignometric Identities? (C2) watch

1. We're using the CGP Textbooks for AQA, and although it gives the answer to this question in the back, it gives quite a lot of leaps and doesn't really explain it self very well.

Show that (tan(x)+1)(tan(x)-1) is identical to (1/cos^2(x)) - 2

I get to (1-cos^2(x)/cos^2(x)) -1 and then I'm completely lost as to how you manage to get to
(1/cos^2(x)) - 2

I would appreciate any help haha
2. (Original post by CoreyRobertson)
...
3. (Original post by Zacken)
That's my problem, I don't get the jump you made int he second step at all... it seems like you just added numbers
4. (Original post by CoreyRobertson)
That's my problem, I don't get the jump you made int he second step at all... it seems like you just added numbers
Do you agree that if I have this is the same thing as ?
5. (Original post by Zacken)
Do you agree that if I have this is the same thing as ?
ahhh thanks, I think I see it now, cheers for the help
6. (Original post by CoreyRobertson)
ahhh thanks, I think I see it now, cheers for the help
Great! No problem.
7. I would just notice that it is difference of 2 squares. The 2 brackets multiply to give .

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