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 February 8th, 2013, 07:25 PM #1 Newbie   Joined: Feb 2013 Posts: 5 Thanks: 0 How can I find the angle X [a*cos(b-X)]^2 = c*cos(X) where a, b, c are constant February 8th, 2013, 10:19 PM #2 Senior Member   Joined: Dec 2012 Posts: 148 Thanks: 0 Re: How can I find the angle X I am not sure about this problem... Could you check if you posted it right?! February 9th, 2013, 01:25 AM #3 Newbie   Joined: Feb 2013 Posts: 5 Thanks: 0 Re: How can I find the angle X HI Yes it is OK. There is one unknown and one equation and I am stuck in solving the angle X. February 9th, 2013, 01:46 AM #4 Newbie   Joined: Feb 2013 Posts: 5 Thanks: 0 Re: How can I find the angle X Or alternatively I want to find the solution of equation given below [a*cos(x)]^2 + b*sin(x)*cos(x) + c = cos(x) where a, b and c are constant Thanks. February 9th, 2013, 10:22 PM #5 Senior Member   Joined: Dec 2012 Posts: 148 Thanks: 0 Re: How can I find the angle X Put random numbers for a, b, c (radians), try to solve and then generalize for a, b, c. February 9th, 2013, 10:35 PM   #6
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Re: How can I find the angle X

Quote:
 Originally Posted by Yasir [a*cos(b-X)]^2 = c*cos(X) where a, b, c are constant
Hint : Expand cos(b-x) and try writing the whole equation in terms of cos(x). It will result a quartic equation. Solving it and handling the periods would be sufficient for finding 'x'.

Quote:
 Originally Posted by tahir.iman Put random numbers for a, b, c (radians), try to solve and then generalize for a, b, c.
Wha? Why would one do that?? February 9th, 2013, 11:50 PM #7 Newbie   Joined: Feb 2013 Posts: 5 Thanks: 0 Re: How can I find the angle X Thanks a lot for your help. I am trying to solve this its not as simple as it looks like e.g. i am not able to find quadratic equation with only cos(x) term. February 10th, 2013, 01:10 AM   #8
Math Team

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From: India, West Bengal

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Math Focus: Number Theory
Re: How can I find the angle X

Quote:
 Originally Posted by Yasir i am not able to find quadratic equation
I didn't said quadratic, did I? I said 'quartic'. A polynomial of degree 4. February 10th, 2013, 03:07 AM #9 Newbie   Joined: Feb 2013 Posts: 5 Thanks: 0 Re: How can I find the angle X Thanks for the clarification. I will try again to write whole equation in terms of cos(x). Previously I was ended up with an equation having one extra sin(x) term. I will try again to get rid of sin(x). Thanks. February 10th, 2013, 03:16 AM #10 Math Team   Joined: Mar 2012 From: India, West Bengal Posts: 3,871 Thanks: 86 Math Focus: Number Theory Re: How can I find the angle X Try the Pythagoras theorem for writing out sin(x) in terms of cos(x), the whole calculation can get a bit messy . . . Tags angle, find Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Threads Thread Thread Starter Forum Replies Last Post masterofmath Algebra 2 August 23rd, 2013 02:42 AM Albert.Teng Algebra 4 February 20th, 2013 05:04 AM mariasp Complex Analysis 7 October 22nd, 2012 05:40 AM zgonda Algebra 9 August 22nd, 2010 05:48 PM naserellid Algebra 6 August 15th, 2010 03:54 PM

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