February 28th, 2016, 01:38 PM  #1 
Newbie Joined: Feb 2016 From: washington Posts: 4 Thanks: 0  Prove Question
I can't seem to get the answer but I think I'm close. The question is sin^4(x)  cos^4(x) = 1  2cos^2(x) I got sin^2(x)cos^2(x)/sin^2(x)+cos^2(x), trying to prove LHS. Thanks ! 
February 28th, 2016, 01:50 PM  #2 
Math Team Joined: Jul 2011 From: Texas Posts: 3,016 Thanks: 1600 
$\sin^4{x}\cos^4{x}=$ $(\sin^2{x}\cos^2{x})(\sin^2{x}+\cos^2{x})=$ $(\sin^2{x}\cos^2{x}) \color{red}{(1)}=$ $(1\cos^2{x})\cos^2{x}=$ $12\cos^2{x}$ Last edited by skeeter; February 28th, 2016 at 02:08 PM. 

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