View Full Version : Trig question
aussie_kris
May 8, 2005, 11:58 PM
Hey
how do I solve
2cos^2($) + sin ($) = 1
Any help would be great
aussie_kris
May 9, 2005, 03:15 AM
Hey I need to solve it for theta -pie to pie
aussie_kris
May 9, 2005, 03:57 AM
Hey thanks
I think that's what I need
also any hints with expressing cos3($) in terms of sin and sin3($) in terms of cos??
aussie_kris
May 9, 2005, 04:02 AM
How did u get 5.176?? I got -63.435
shanus
May 9, 2005, 07:47 AM
Ahhhh... I hate to burst eveyone's bubble here, but...
Cos2($) is not equal to 2x/r
i.e.. Cos2($) is not equal to 2Cos($)
I think a lot of Mathematicians would be upset if this were true ;)
MathMaven53
Jun 29, 2005, 01:38 PM
Let's express the equation in terms of Sin(x)
We have 2 Cos^2 (x) + Sin(x) =1
We use Cos^2 (x) = 1 - Sin^2(x)
After substituting and simplifying we get the equation
2 Sin^2(x) - Sin(x) - 1 = 0
Factor this into
(2Sin(x) + 1)(Sin(x) -1) = 0
Now set each factor equal to zero,solve for Sin(x) and then x