\(f(x)=\frac{1}{4}tg8x+\sqrt2.\) Найдите \(f'(x).\)

• \(-\frac{2}{cos^28x}\)
• \(\frac{8}{cos^28x}+\frac{1}{2\sqrt2}\)
• \(\frac{1}{cos^28x}\)
• \(\frac{2}{cos^28x}\)