The number of real roots of the equation $1+\cos ^2x+\cos ^3 x – \cos^4x=5$ is equal to
Any idea how this could be done??
To make equation satisfy, $cos^2 x +cos^3 x - cos^4 x = 4$ but $-1 \leq cosx \leq +1$. Here, we can't make sum $= 4$ for any real value of $x$. So, no real $x$ exists.