SOLUTION: I need help solving the following equation for 0(<=) X (<=)2pi 2cos^2X - 3cosX-2=0 Thank you!

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Question 337025: I need help solving the following equation for 0(<=) X (<=)2pi
2cos^2X - 3cosX-2=0
Thank you!
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Use a substitution,
u=cos%28x%29
2u%5E2-3u-2=0
%282u%2B1%29%28u-2%29=0
Two solutions:
2u%2B1=0
2u=-1
u=-1%2F2
cos%28x%29=-1%2F2
x=%282%2Api%29%2F3, %284%2Api%29%2F3
.
.
.
u-2=0
u=2
cos%28x%29=2
No solutions.