你为什麽不一次问几题呀?
∫(0→π/4) tan⁴θ dθ
= ∫(0→π/4) tan²θ(sec²θ - 1) dθ,1 + tan²x = sec²x
= ∫(0→π/4) tan²θsec²θ dθ - ∫(0→π/4) tan²θ dθ
= ∫(0→π/4) tan²θ d(tanθ) - ∫(0→π/4) (sec²θ - 1) dθ
= [(1/3)tan³θ - tanθ + θ] |(0→π/4)
= 1/3 - 1 + π/4
= π/4 - 2/3