※ 引述《tavern (zzzzzzz)》之銘言:
: https://i.imgur.com/GHTqCVr.jpg
: 請問根號裡面是怎麼從紅筆第一行變成第二行的,謝謝
2θ = t
(1/2)sin(2θ)√[1 - (1/2)(sin(2θ))^2] dθ
= (1/4)sin(t)√[1 - (1/2)(sint)^2] dt
= (1/√2)(1/4)sin(t)√[1 + cos(t)^2] dr
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