Trig. Identities...

Are you new to HelpingTeens.org? Feel free to stop in here and introduce yourself! Have a question that doesn't seem to fit anywhere else? Post it here.
Post Reply
User avatar
SirPostAlot
Veteran
Posts: 8532
Joined: Sat May 10, 2003 7:28 pm

Trig. Identities...

Post by SirPostAlot »

Ok...

the trig identity "pathagorian identity"



ok just to clearify...when i have sin(^2)x that is sin squared....NOT sin raised to the 2x...ok?



well it states:



1 - sin(^2)x = cos(^2)



so...



is



1 - sin(^4)x = cos(^4)



???



Thanks!!



Super needed!!



~Jeff~
User avatar
Gostridah
Loyal
Posts: 265
Joined: Mon Jul 28, 2003 7:59 pm
Contact:

Re: Trig. Identities...

Post by Gostridah »

Let's rewrite those as



a. sin(^2)x+cos(^2)x=1,



b. sin(^4)x+cos(^4)x=1 (?)



If in a we square both sides, we get:



(sin(^2)x+cos(^2)x)^2=1^2=1, so



sin(^4)x+2.sin(^2)x.cos(^2)x+cos(^4)x=1, so



sin(^4)x+cos(^4)x=1-2.sin(^2)x.cos(^2)x, which isn't 1 unless sinx or cosx is 0.
User avatar
SirPostAlot
Veteran
Posts: 8532
Joined: Sat May 10, 2003 7:28 pm

Re: Trig. Identities...

Post by SirPostAlot »

hmm...yeah i think i see what your saying...



okies i understand...haha



thanks!



:hug:



~Jeff~
Post Reply