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March 7th, 2010, 12:47 PM  #1 
Newbie Joined: Mar 2010 Posts: 16 Thanks: 0  finding exact values of trig equations
I can find the exact values for simple equations like , but when they look like this I have a litte trouble. I tried to solve the second one and i got 2pi/18 as a solution. It actually seemed to work, but I'm not sure if its right. Also once I find one solution how do I get the second solution. 
March 7th, 2010, 01:03 PM  #2 
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 7,958 Thanks: 1146 Math Focus: Elementary mathematics and beyond  Re: finding exact values of trig equations We know that and equal 1/2 so you want to solve and for x. 
March 7th, 2010, 01:52 PM  #3 
Newbie Joined: Mar 2010 Posts: 16 Thanks: 0  Re: finding exact values of trig equations
Well I tried doing what you said and my two answers are pi/18 and 9pi/18. When I enter them in for x they equal 0 so I think they work. 
March 7th, 2010, 02:17 PM  #4 
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 7,958 Thanks: 1146 Math Focus: Elementary mathematics and beyond  Re: finding exact values of trig equations
Your solutions are correct. 9pi/18 is pi/2.

March 7th, 2010, 02:43 PM  #5 
Newbie Joined: Mar 2010 Posts: 16 Thanks: 0  Re: finding exact values of trig equations
Ok thanks. In some of the problems I have instead of them being in radians they are in degrees and I don't know how this changes the way I should solve it. For example, 3sec(4x+10degrees)=9 
March 8th, 2010, 03:12 AM  #6 
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 7,958 Thanks: 1146 Math Focus: Elementary mathematics and beyond  Re: finding exact values of trig equations
cos(4x + 10) = 1/3

March 8th, 2010, 08:00 AM  #7  
Senior Member Joined: Apr 2008 Posts: 435 Thanks: 0  Re: finding exact values of trig equations Quote:
 
March 8th, 2010, 10:18 AM  #8  
Senior Member Joined: Mar 2007 Posts: 428 Thanks: 0  Re: finding exact values of trig equations Quote:
 
March 8th, 2010, 11:26 AM  #9  
Newbie Joined: Mar 2010 Posts: 16 Thanks: 0  Re: finding exact values of trig equations Quote:
When changing the equation from sec to cos what did you do to the 3 to change it to 1/3.  
March 8th, 2010, 11:37 AM  #10 
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 7,958 Thanks: 1146 Math Focus: Elementary mathematics and beyond  Re: finding exact values of trig equations
3sec(4x + 10) = 9 sec(4x + 10) = 3 1/cos(4x + 10) = 3 1 = 3cos(4x + 10) 1/3 = cos(4x + 10) 

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