Tìm nguyên hàm \(F\left(x\right)\)
\(F\left(x\right)=\tan x2\cot x-\sqrt{2}\cos x+2\cos^2xdx=2-\sqrt{2}\sin x+\sin2xdx\)\(=2x+\sqrt{2}\cos x-\frac{\cos2x}{2}+C\)
\(F\left(\frac{\pi}{4}\right)=2.\frac{\pi}{4}+\sqrt{2}+\frac{\sqrt{2}}{2}-0+C=\frac{\pi}{2}\Rightarrow C=-1\)
Vậy \(F\left(x\right)=2x+\sqrt{2}\cos x-\frac{\cos2x}{2}-1\)