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trig!!!! :(

ok, ive got a question and im slightly stuck:
using the identity cos^2x+sin^2x=1, prove that tan^2x=sec^2x-1

any ideas on how to do it?? please

cheers guys
Original post by Alice Moody
ok, ive got a question and im slightly stuck:
using the identity cos^2x+sin^2x=1, prove that tan^2x=sec^2x-1

any ideas on how to do it?? please

cheers guys


I would start off by remembering this:

sec2(x)=1cos2(x)sec^{2}(x)=\frac{1}{cos^{2}(x)}

See if you can incorporate this into cos2(x)+sin2(x)=1cos^{2}(x)+sin^{2}(x)=1.
Reply 2
Original post by rayquaza17
I would start off by remembering this:

sec2(x)=1cos2(x)sec^{2}(x)=\frac{1}{cos^{2}(x)}

See if you can incorporate this into cos2(x)+sin2(x)=1cos^{2}(x)+sin^{2}(x)=1.

thank you. for some reason, i thought you could do that, i thought it was only secx=1/cosx

thank you!!!! :smile:
Original post by Alice Moody
ok, ive got a question and im slightly stuck:
using the identity cos^2x+sin^2x=1, prove that tan^2x=sec^2x-1

any ideas on how to do it?? please

cheers guys


Moved to Maths section :smile:
Reply 4
Original post by MathsNerd1
Moved to Maths section :smile:

what maths section? im still getting used to being on here :smile:
Original post by Alice Moody
what maths section? im still getting used to being on here :smile:


This maths section

We are in study help
Original post by Alice Moody
what maths section? im still getting used to being on here :smile:


You originally posted this in the a-level section. If you post maths questions in the maths section (http://www.thestudentroom.co.uk/forumdisplay.php?f=38), you will be more likely to get help. :smile:
Reply 7
ok, ive got a question and im slightly stuck:
using the identity cos^2x+sin^2x=1, prove that tan^2x=sec^2x-1

any ideas on how to do it??

cheers guys
Reply 8
Okay!!! thank you ever so much!!
Divide through by cos^(2)x

Rearrange

Posted from TSR Mobile
Reply 10
Original post by Alice Moody
ok, ive got a question and im slightly stuck:
using the identity cos^2x+sin^2x=1, prove that tan^2x=sec^2x-1

any ideas on how to do it??

cheers guys


Isn't this the very same question you originally posted in another thread?

I think your question has been answered, but see what happens when you divide your original identity by cos2x\cos^2 x
Original post by QuantumSuicide
Divide through by cos^(2)x

Rearrange

Posted from TSR Mobile

why do i always overcomplicate stuff? thatt was such an easy question! thank you!!!! :biggrin:
Original post by davros
Isn't this the very same question you originally posted in another thread?

I think your question has been answered, but see what happens when you divide your original identity by cos2x\cos^2 x

yes it is, but was told to put it in the maths section? they said i would probably get more answers! but thank you :smile:
Reply 13
Original post by Alice Moody
yes it is, but was told to put it in the maths section? they said i would probably get more answers! but thank you :smile:



For future questions, yes! In this case, one of the Moderators moved your original thread into the Maths section so other people could see it :smile:
Original post by davros
For future questions, yes! In this case, one of the Moderators moved your original thread into the Maths section so other people could see it :smile:

oh right!! haha didnt know that!! sorry :frown: hahaha :biggrin:

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