(sinx/4)^4 求导(sinx/4)^4+(cosx/4)^4 求导

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(sinx/4)^4 求导
(sinx/4)^4+(cosx/4)^4 求导

答:
[(sinx/4)^4 ]'
=4*[(sinx/4)^3]*[sinx/4]'
=4*[(sinx/4)^3]*(1/4)cos(x/4)
=[(sinx/4)^3]*cos(x/4)
(sinx/4)^4+(cosx/4)^4
=[(sinx/4)^2+(cosx/4)^2]^2-2[(sinx/4)(cosx/4)]^2
=1-(1/2)(sinx/2)^2
=1-(1/2)*(1/2)(1-cosx)
=3/4+(1/4)cosx
求导:
[(sinx/4)^4+(cosx/4)^4]'
=[3/4+(1/4)cosx]'
=-(1/4)sinx