1 votes 1 votes The number of real roots of the equation $1+\cos ^2x+\cos ^3 x – \cos^4x=5$ is equal to $0$ $1$ $3$ $4$ Quantitative Aptitude isi2014-dcg quantitative-aptitude trigonometry roots + – Arjun asked Sep 23, 2019 recategorized Nov 12, 2019 by Lakshman Bhaiya Arjun 543 views answer comment Share Follow See all 4 Comments See all 4 4 Comments reply `JEET commented Sep 29, 2019 i moved by `JEET Sep 30, 2019 reply Follow Share Is $4$ the answer?? 0 votes 0 votes `JEET commented Oct 5, 2019 reply Follow Share @ankitgupta.1729 Any idea how this could be done?? 0 votes 0 votes ankitgupta.1729 commented Oct 5, 2019 reply Follow Share @`JEET 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. 1 votes 1 votes `JEET commented Oct 5, 2019 reply Follow Share Thanks. 1 votes 1 votes Please log in or register to add a comment.
0 votes 0 votes 0 real roots of the equation as the maximum value cos x can take is 1 and then LHS of equation will become 2. LHS can never become 5. mudit23june answered Jan 25, 2020 mudit23june comment Share Follow See all 0 reply Please log in or register to add a comment.