[求助] 求正弦曲线长度过程，或者如图所示积分求解过程，要详细不要电脑软件计算

4楼: Originally posted by 听mayday at 2017-08-14 19:56:38
手机看不到图片
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3楼: Originally posted by alober at 2017-08-14 17:06:54
I \mathop{=}^{2x \to x} \frac{1}{2}\int_{0}^{2}\sqrt{1+4\cos^2x}dx = \frac{1}{2}\int_{0}^{2}\sqrt{5-4\sin^2x}dx = \frac{\sqrt{5}}{2}\int_{0}^{2}\sqrt{1-(\sqrt{\frac{4}{5}}\sin x)^2}dx = \frac{\sqrt{5 ...