求sqrt(360/x)*sin(x)的最大值~~ 請附過程,謝謝~~?

2017-10-31 8:03 pm
更新1:

最後面應該是"!"

更新2:

x的值大約是66.78

回答 (1)

2017-11-01 1:22 pm
✔ 最佳答案
f(x)=sqrt(360/x)*sin(x)
=(360)^(1/2)*x^(-1/2)* sin x
f'(x)=(360)^(1/2)*[(-1/2)*x^(-3/2)*sin x + x^(-1/2)*cos x]
=(360)^(1/2)*x^(-1/2)*[(-1/2)*x^(-1)*sin x + cos x]
f'(x)=0 時有最大值, (-1/2)*x^(-1)*sin x + cos x = 0
tan x - 2x = 0 ---> x ~ 66.78 度 (x要以弳度表示)

f(x)=sqrt(360/x)*sin(x)
f(66.78)~16.15116


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