The general solution of the equation 2cos2x=3.2cos²x-4 is?

1 Answer
Jun 22, 2018

No real solution.

Explanation:

#2cos2x=3.2cos^2 x -4#
#2cos2x=16/5cos^2 x-4|-(16/5cos^2 x-4)#
#2cos2x-16/5cos^2(x)+4=0|* 5/2#
#5cos2x-8cos^2(x)+10=0#
#color(blue)(cos(2x)=2cos^2(x)-1)#
#5 * (color(blue)(2cos^2(x)-1))-8cos^2(x)+10=0#
#2cos^2(x)+5=0#
#cos^2(x)=-5/2#
#cos(x)=sqrt(-5/2)#
There is no real solution since the radicand is negative.