Find all solutions of the equation in the interval 0 2pi 2
Find all solutions of the equation in the interval [ 0, 2pi )
2sin2x = 2 - cosx
Write your answer in radians in terms of pi. If there is more than one solution, separate them with commas.
Solution
2sin^2x = 2 - cosx
as we know sin^2x +cos^2x =1
So, 2( 1-cos^2x) = 2 -cosx
2 -2cos^2x = 2 -cosx
-2cos^2x +cosx =0
cosx( 1 -2cosx) =0
cosx =0
x= pi/2, 3pi/2
1-2cosx =0 ; cosx =1/2
x= cos^-1(1/2) = pi/3, 2pi-pi/3
= pi/3 , 5pi/3
Solution in the interval [ 0, 2pi ) : x= pi/2 , pi/3 , 3pi/2 , 5pi/3
