请问这道题怎么做啊
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令x=√2sect,则dx=√2secttantdt
原式=∫(√2secttant)/[(√2sect-1)√2tant]dt
=∫sect/(√2sect-1)dt
=∫dt/(√2-cost)
令u=tan(t/2),则cost=(1-u^2)/(1+u^2),dt=2du/(1+u^2)
原式=∫[2/(1+u^2)]/[√2-(1-u^2)/(1+u^2)]du
=∫2/[(√2+1)u^2+√2-1]du
=(2√2-2)*∫du/[u^2+(√2-1)^2]
=2arctan[(√2+1)u]+C
=2arctan[(√2+1)tan(t/2)]+C
=2arctan[(√2+1)(csct-cott)]+C
=2arctan[(√2+1)(x-√2)/√(x^2-2)]+C,其中C是任意常数
原式=∫(√2secttant)/[(√2sect-1)√2tant]dt
=∫sect/(√2sect-1)dt
=∫dt/(√2-cost)
令u=tan(t/2),则cost=(1-u^2)/(1+u^2),dt=2du/(1+u^2)
原式=∫[2/(1+u^2)]/[√2-(1-u^2)/(1+u^2)]du
=∫2/[(√2+1)u^2+√2-1]du
=(2√2-2)*∫du/[u^2+(√2-1)^2]
=2arctan[(√2+1)u]+C
=2arctan[(√2+1)tan(t/2)]+C
=2arctan[(√2+1)(csct-cott)]+C
=2arctan[(√2+1)(x-√2)/√(x^2-2)]+C,其中C是任意常数
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