
Trigonometry Trigonometry Math Forum 
 LinkBack  Thread Tools  Display Modes 
January 24th, 2012, 01:30 AM  #1 
Newbie Joined: Jan 2012 Posts: 9 Thanks: 0  Trigonometric inequalities problem
So I have problem solving this two trigonometric inequalities sinx+cox+sin2x>1 tg(x+pi/5)<sqrt(3) Please help and if you can post the procedure of solving this inequalities 
January 24th, 2012, 02:31 AM  #2  
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 7,842 Thanks: 1068 Math Focus: Elementary mathematics and beyond  Re: Trigonometric inequalities problem Quote:
 
January 24th, 2012, 02:45 AM  #3  
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 7,842 Thanks: 1068 Math Focus: Elementary mathematics and beyond  Re: Trigonometric inequalities problem Quote:
 
January 24th, 2012, 03:05 AM  #4 
Newbie Joined: Jan 2012 Posts: 9 Thanks: 0  Re: Trigonometric inequalities problem
oh,its cosx 
January 24th, 2012, 10:22 AM  #5 
Senior Member Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,193 Thanks: 504 Math Focus: Calculus/ODEs  Re: Trigonometric inequalities problem
We are given: Solving the quadratic equation: Assuming x is real, we must discard the root whose magnitude is greater than 1, so we have: Checking the interval given by: Using , we find by substitution into the quadratic inequality: Thus, we find: where 
January 24th, 2012, 03:27 PM  #6 
Newbie Joined: Jan 2012 Posts: 9 Thanks: 0  Re: Trigonometric inequalities problem
THANK YOU 
January 24th, 2012, 05:44 PM  #7  
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 7,842 Thanks: 1068 Math Focus: Elementary mathematics and beyond  Re: Trigonometric inequalities problem Quote:
These values can be obtained by solving  
January 25th, 2012, 01:06 AM  #8 
Newbie Joined: Jan 2012 Posts: 9 Thanks: 0  Re: Trigonometric inequalities problem
Ok,so I have these two more inequalities to solve and Im done 2sinx*sin2x*sin3x<sin4x sinx*cos5x<sin9x*cos3x 
January 25th, 2012, 01:17 AM  #9 
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 7,842 Thanks: 1068 Math Focus: Elementary mathematics and beyond  Re: Trigonometric inequalities problem
Have you made any attempt at solving them?

January 25th, 2012, 01:37 AM  #10 
Newbie Joined: Jan 2012 Posts: 9 Thanks: 0  Re: Trigonometric inequalities problem
Yes I did for the first one I come to this sin2xcos3xcosx>0 and for the second one sin12x>sin4x and dont know how to solve it further


Tags 
inequalities, problem, trigonometric 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
inequality problem and inequalities  AndresDM  Algebra  3  November 14th, 2013 12:59 PM 
Trigonometric Identity Problem...  perfect_world  Trigonometry  4  August 7th, 2013 01:52 PM 
trigonometric inequalities  Bencz  Trigonometry  9  April 30th, 2013 05:10 AM 
I am stuck in this trigonometric problem.  dennisdixon  Trigonometry  2  April 29th, 2013 08:20 PM 
Probability Word Problem Involving Inequalities  julian21  Probability and Statistics  3  April 8th, 2011 08:51 PM 