My Math Forum Solve equation

 Algebra Pre-Algebra and Basic Algebra Math Forum

 March 11th, 2011, 09:33 AM #1 Member   Joined: Feb 2009 Posts: 54 Thanks: 0 Solve equation $cos 2x + cos x= sin^2 x$ All Ive got so far is $cos^2 x - sin^2 x + cos x= sin^2 x$
 March 11th, 2011, 10:25 AM #2 Global Moderator     Joined: Nov 2009 From: Northwest Arkansas Posts: 2,766 Thanks: 4 Re: Solve equation So far, so good. Now replace sin^2(x) with 1 - cos^2(x) in both places, and you should get a quadratic equation "in cos(x)". ie, if you sub U = cos(x), you'll be able to rewrite as aU^2 + bU + c = 0 and solve by usual methods.
 March 11th, 2011, 06:47 PM #3 Senior Member   Joined: Apr 2007 Posts: 2,140 Thanks: 0 Tank271, this should be very easy to solve if you know the trigonometric identities cos 2x = cos²x - sin²x and sin²x + cos²x = 1.

 Tags equation, solve

 Thread Tools Display Modes Linear Mode

 Similar Threads Thread Thread Starter Forum Replies Last Post Shamieh Algebra 6 May 21st, 2013 09:46 PM mmmmxxx Algebra 3 September 4th, 2012 06:22 PM boomer029 Algebra 8 March 17th, 2012 05:09 PM ishoothigh Algebra 1 December 14th, 2011 08:09 AM sagelady Calculus 2 July 24th, 2011 08:35 PM

 Contact - Home - Forums - Cryptocurrency Forum - Top