April 23rd, 2009, 10:30 AM  #1 
Newbie Joined: Apr 2009 Posts: 3 Thanks: 0  Trig Interval Question
I solved each problem, so if someone can check them I would appreciate it! 1. Solve the equation in the interval [0,2pi) tanxcosxcosx=0 I found all solutions of the equation to be Cos: pi/2 +2npi ; 3pi/2 + 2npi The problem is both yield error when plugging into a calc so do I just exclude? n is any integer Tan: pi/4 +npi (this is just pi instead of 2pi because one period of tan is from (pi/2, pi/2) If the question asks for the solutions in the interal [0,2pi) then the answers would just be pi/4? 2. Solve the equation in the interval [0,2pi) 2 cos^2x+sinx=1 For all solutions of the above I got 7pi/6 + 2npi; 11pi/6 + 2npi; pi/2 + 2npi So, for the interval [0,2pi] would it just be pi/2, 7pi/6, 11pi/6 
April 23rd, 2009, 10:42 AM  #2 
Newbie Joined: Apr 2009 Posts: 3 Thanks: 0  Re: Trig Interval Question
Here is some additional work for #1 and #2 1. tanxcosxcosx=0 cosx(tanx1)=0 cosx=0 thus x is pi/2 and 3pi/2 but when checked yields error tanx=1 @pi/4 2. 2cos^2x+sinx=1 2(1sin^2x)+sinx1=0 22sin^2x+sinx1=0 2sin^2x+sinx+1=0 1(2sinx+1)(sinx1)=0 2sinx+1=0 sin x=1/2 @7pi/6 and 11pi/6 sinx1=0 sin x =1 @pi/2 

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