July 3rd, 2013, 12:23 AM  #1 
Newbie Joined: Jul 2013 Posts: 1 Thanks: 0  straight lines
Find the equation of straight lines which passes through the point (1,2) and makes an angle theta with the positive direction of the xaxis, where cos (theta) = 1/3.
Last edited by skipjack; September 4th, 2015 at 02:59 AM. 
July 3rd, 2013, 12:31 AM  #2 
Senior Member Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 521 Math Focus: Calculus/ODEs  Re: straight lines
What is the relationship between the angle of inclination and the slope of the line?

September 4th, 2015, 02:58 AM  #3 
Senior Member Joined: Sep 2015 From: 4th Dimension Posts: 146 Thanks: 13 Math Focus: Everything (a little bit) 
A =(theta) Cos A = 1/3 Therefore Tan A = 8^(1/2)=m (slope of line ) (Y2/x1)=m=8^(1/2) Hence, 2(2^(1/2))x  y  2(2^(1/2)) + 2 =0 
September 4th, 2015, 03:03 AM  #4 
Global Moderator Joined: Dec 2006 Posts: 20,927 Thanks: 2205 
As the question doesn't say otherwise, tan(θ) can be positive or negative.

September 4th, 2015, 06:29 AM  #5 
Senior Member Joined: Sep 2015 From: 4th Dimension Posts: 146 Thanks: 13 Math Focus: Everything (a little bit)  
September 4th, 2015, 06:35 AM  #6 
Senior Member Joined: Sep 2015 From: 4th Dimension Posts: 146 Thanks: 13 Math Focus: Everything (a little bit)  

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