SOLUTION: if cos2x+3cosx-1= 0
then x=?
I got pi/2 for some reason the answer is pi/3 WHY?
Thanks in advance!
Algebra.Com
Question 882227: if cos2x+3cosx-1= 0
then x=?
I got pi/2 for some reason the answer is pi/3 WHY?
Thanks in advance!
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
if cos2x+3cosx-1= 0
then x=?
I got pi/2 for some reason the answer is pi/3 WHY?
---------------------------
2cos^2(x)-1 + 3cos(x) -1 = 0
2cos^2(x) + 3cos(x) - 2 = 0
Factor:
(2cos(x)-1)(cos(x)+2) = 0
cos(x) = 1/2
cos(x = -2 (extraneous)
====
x + pi/3 or pi = -pi/3
=========================
Cheers,
Stan H.
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