Answer:
The answer is the first one ⇒ [tex]\frac{1-2cos2x+\frac{1+cos4x}{2}}{4}[/tex]
Step-by-step explanation:
∵ cos4x = 2cos²2x - 1
∴ cos²2x = (1 + cos4x)/2
∴ [tex]sinx^{4}x=\frac{1-2cos2x+\frac{1+cos4x}{2}}{4}[/tex] ⇒ ×2 up and down
[tex]=\frac{2-4cos2x+1+cos4x}{8}[/tex]
[tex]=\frac{3-4cos2x+cos4x}{8}[/tex]
