Determine the range of the function f(x)=sin4(x)+cos4(x)f(x) = \sin^4(x) + \cos^4(x)f(x)=sin4(x)+cos4(x).
[0,1][0, 1][0,1]
[1/2,1][1/2, 1][1/2,1]
[1/4,1][1/4, 1][1/4,1]
[0,1/2][0, 1/2][0,1/2]