Question

cos^2x-cos2x=-3/4

Answer 1

\[\cos ^{2}x-\cos 2x=-\frac{ 3 }{ 4 }\]
\[2\cos ^{2}x=1+\cos 2x\]
\[2\cos ^{2}x-2\cos 2x=-\frac{ 3 }{ 2 }\]
\[1+\cos 2x-2\cos 2x=-\frac{ 3 }{2},1-\cos 2x=-\frac{ 3 }{ 2 },\cos 2x=1+\frac{ 3 }{2 }=\frac{ 5 }{2}\]
which is impossible.
Either i am wrong or statement is wrong.
Otherwise
\[\cos ^{2}x-\left( \cos ^{2}x -\sin ^{2}x\right)=-\frac{ 3 }{4 }\]
or \[\sin ^{2}x=-\frac{ 3 }{4 },which is impossible.\]
Hence statement is wrong.