有关高等数学的问题
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令x=2sint,dx=2costdt
x=0时,t=0;x=2时,t=π/2.
原式=∫[0,π/2]4sin²t · 2cost · 2costdt
=16∫[0,π/2]sin²t cos²t dt
=4∫[0,π/2](2sintcost)² dt
=4∫[0,π/2]sin²(2t) dt
=2∫[0,π/2][1-cos(4t)]dt
=2[t - 1/4 sin(4t)]|[0,π/2]
=2×(π/2 -0)
=π
x=0时,t=0;x=2时,t=π/2.
原式=∫[0,π/2]4sin²t · 2cost · 2costdt
=16∫[0,π/2]sin²t cos²t dt
=4∫[0,π/2](2sintcost)² dt
=4∫[0,π/2]sin²(2t) dt
=2∫[0,π/2][1-cos(4t)]dt
=2[t - 1/4 sin(4t)]|[0,π/2]
=2×(π/2 -0)
=π
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谢谢老师
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