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 Post subject: Help proving trig identitiesPosted: Thu, 5 Apr 2012 21:02:26 UTC

Joined: Thu, 5 Apr 2012 20:56:32 UTC
Posts: 7
Hello. I need some help solving these trig identities. It's really important that I understand HOW the answers are reached. The teacher said the assignment would be just like what we did in class, but i think he lied..

sec^4(x)-tan^4(x)=sec^2(x)+tan^2(x)

For this problem, the fourth power confuses me, would I take a squareroot of the first side to bring it down to a square?

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 Post subject: Re: Help proving trig identitiesPosted: Thu, 5 Apr 2012 21:56:21 UTC
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Joined: Fri, 1 Jul 2011 01:17:26 UTC
Posts: 322
supersam1130 wrote:
Hello. I need some help solving these trig identities. It's really important that I understand HOW the answers are reached. The teacher said the assignment would be just like what we did in class, but i think he lied..

sec^4(x)-tan^4(x)=sec^2(x)+tan^2(x)

For this problem, the fourth power confuses me, would I take a squareroot of the first side to bring it down to a square?

You need to use sec^4 - tan^4 = (sec^2 + tan^2)(sec^2 - tan^2). The rest should be very easy.

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 Post subject: Re: Help proving trig identitiesPosted: Thu, 5 Apr 2012 22:06:56 UTC

Joined: Thu, 5 Apr 2012 20:56:32 UTC
Posts: 7
Thank you!

Last edited by supersam1130 on Thu, 5 Apr 2012 22:08:26 UTC, edited 1 time in total.

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 Post subject: Re: Help proving trig identitiesPosted: Thu, 5 Apr 2012 22:07:25 UTC
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Joined: Wed, 30 Mar 2005 04:25:14 UTC
Posts: 12103
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supersam1130 wrote:
Thank you! Could you tell me why, when you break down sec^4 - tan^4 it becomes (sec^2 + tan^2)(sec^2 - tan^2)? I don't understand why there is a sec and a tan in each of the parenthesis

You learned back in algebra 1 or 2 that

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 Post subject: Re: Help proving trig identitiesPosted: Thu, 5 Apr 2012 22:09:32 UTC

Joined: Thu, 5 Apr 2012 20:56:32 UTC
Posts: 7
I realized that a second after I posted that reply, then I tried changing it... haha..
These problems scare me so much I get nervous and over think them. I really appreciate your help. <3

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