Question 310844: solve over the interval [0,2pi), 2 cos^2x=4cosx-2
Answer by nyc_function(2741)   (Show Source):
You can put this solution on YOUR website! Treat it as a regular quadratic equation but in trig form.
2cos^2x = 4cosx - 2
Bring everything to the left side and then equate to zero.
2cos^2x - 4cosx + 2 = 0
Apply the rules for solving a quadratic equation to find cosx.
Can you finish now?
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I got your reply. Did you get my reply to this question?
I simply substituted u for cosx to make the factoring using the quadratic formula a lot easier. I found the answer for u to be 1. Then replacing u with cosx, I set cosx = 1. I know that 0 degrees and 2pi radians (which is the same thing as 360 degrees) is the only solution to your trig equation in quadratic form.
Understand?
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