My Math Forum  

Go Back   My Math Forum > High School Math Forum > Pre-Calculus

Pre-Calculus Pre-Calculus Math Forum


Thanks Tree2Thanks
  • 2 Post By skeeter
Reply
 
LinkBack Thread Tools Display Modes
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 !
rxyhme is offline  
 
February 28th, 2016, 01:50 PM   #2
Math Team
 
skeeter's Avatar
 
Joined: Jul 2011
From: Texas

Posts: 2,945
Thanks: 1552

$\sin^4{x}-\cos^4{x}=$

$(\sin^2{x}-\cos^2{x})(\sin^2{x}+\cos^2{x})=$

$(\sin^2{x}-\cos^2{x}) \color{red}{(1)}=$

$(1-\cos^2{x})-\cos^2{x}=$

$1-2\cos^2{x}$
Thanks from v8archie and Country Boy

Last edited by skeeter; February 28th, 2016 at 02:08 PM.
skeeter is offline  
Reply

  My Math Forum > High School Math Forum > Pre-Calculus

Tags
prove, question



Thread Tools
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
How to prove this question? jiasyuen Calculus 5 December 23rd, 2013 04:58 AM
one prove question 450081592 Applied Math 1 September 15th, 2010 03:35 AM
one prove question 450081592 Linear Algebra 1 February 25th, 2010 02:16 AM
prove question igalep132 Calculus 8 February 7th, 2008 04:36 AM
How to prove this question? jiasyuen Algebra 0 December 31st, 1969 04:00 PM





Copyright © 2019 My Math Forum. All rights reserved.