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f(x) = [x^3.cos(x/2).√(4-x^2)
f(-x) = -f(x)
let
x=2sinu
dx=2cosu du
x=0,u=0
x=2, u=π/2
∫(-2->2) [x^3.cos(x/2) +1/2]. √(4-x^2) dx
=(1/2)∫(-2->2) √(4-x^2) dx
=∫(0->2) √(4-x^2) dx
=4∫(0->π/2) (cosu)^2 du
=2∫(0->π/2) (1+cos2u) du
=2[u+(1/2)sin2u]|(0->π/2)
=π
=3.14159 (前6位)
f(-x) = -f(x)
let
x=2sinu
dx=2cosu du
x=0,u=0
x=2, u=π/2
∫(-2->2) [x^3.cos(x/2) +1/2]. √(4-x^2) dx
=(1/2)∫(-2->2) √(4-x^2) dx
=∫(0->2) √(4-x^2) dx
=4∫(0->π/2) (cosu)^2 du
=2∫(0->π/2) (1+cos2u) du
=2[u+(1/2)sin2u]|(0->π/2)
=π
=3.14159 (前6位)
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