Q9 of 142 Page 11

Write the solution set of the equation (2 cos x + 1) (4 cos x + 5) = 0 in the interval (0, 2 π].

8 cos2x+10 cos x+4 cos x+5=0


8 cos2x+14 cos x+5=0


Solving the quadratic equation, we get,


cos x = -0.5


cos x = cos 120°



So


And when n=1


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