\(d=\dfrac{\left(cos^4\left(x\right)-tanx\right)}{cos\left(2x\right)}:t=\dfrac{dcos\left(2x\right)-cos^4\left(x\right)}{anx};cos\left(2x\right)\ne0,n\ne0\)
\(\left\{{}\begin{matrix}d=\dfrac{\left(cos^4\left(x\right)-tanx\right)}{cos\left(2x\right)}\\\dfrac{cos^4\left(x\right)-tanx}{cos\left(2x\right)}=d\end{matrix}\right.\)
\(\Leftrightarrow\) \(\dfrac{\left(cos^4\left(x\right)-tanx\right)cos\left(2x\right)}{cos\left(2x\right)}=dcos\left(2x\right);cos\left(2x\right)\ne0\)
\(\Leftrightarrow\) \(cos^4\left(x\right)-antx=dcos\left(2x\right);cos\left(2x\right)\ne0\)
\(\Leftrightarrow\) \(cos^4\left(x\right)-antx-cos^4\left(x\right)=dcos\left(2x\right)-cos^4\left(x\right);cos\left(2x\right)\ne0\)
\(\Leftrightarrow\) \(-antx=dcos\left(2x\right)-cos^4\left(x\right);cos\left(2x\right)\ne0\)
\(\Leftrightarrow\) \(\dfrac{-antx}{-anx}=\dfrac{dcos\left(2x\right)}{-anx}-\dfrac{cos^4\left(x\right)}{-anx};cos\left(2x\right)\ne0,n\ne0\)
\(\Rightarrow\) \(suy\) \(ra\) \(:\) \(d=-\dfrac{dcos\left(2x\right)-cos^4\left(x\right)}{-anx};cos\left(2x\right)\ne0,n\ne0\)
