3.\x05A clock is hanging on a wall,with the centre of the cl

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3.\x05A clock is hanging on a wall,with the centre of the clock 4.5 m above the ground.Both the minute hand and the second hand are 13 cm long,while the hour hand is 6 cm long.Assume that t=0 is at 12:00:00.
a.\x05Determine the equations of the sine functions that describe the distance of the top of each hand above the ground as a function of time.
b.\x05Sketch a graph of the sine function of the minute hand.
c.\x05Use the graph to describe the speed at which the height of the tip of the minute hand is changing over time.
d.\x05Determine the arc length of the second hand if the central angle is rad.Round to the hundredth.
d.\x09Determine the arc length of the second hand if the central angle is 八分之五π rad.Round to the hundredth.
对不起忘了这个数字是八分之五π

大体翻译了一下也不知道对不对~看着办了
a 是找出指针顶点离地面高度和时间关系的三个正弦函数（实际答案做出来是余弦函数）
b 是画图
相信楼主米有什么问题
c 用图像来描述分针的顶点在纵坐标上的速度.也就是投影的速度了
很明显,位移已经出来了（a问）,现在求速度,直接求导,over.图像上的解释,就是斜率方程了,作图的话就是余弦变正弦（左移π）
d 这里好像漏掉了一个东西rad前面应该有个数值.大体意思就是说,如果圆心角是xxx,请确定秒针划过的弧长.精确到百分位
直接用长度*角度即可.
再问：可是偶还不会求导......这是我在加拿大12年级遇到的题目马上要考试了发下来的习题果然好难大家讲思路就可以最后最好给个答案（针对d）
再答： c，这个是描述，不是说什么数值的标准答案吧，具体来说一下： minute hand--S(t)=0.13sin(π/1800*t+π/2)+4.5 这个是分针的位移函数（a问求出来了）那么速度函数则是上面那个东西往左平移π/2，既是：V(t)=0.13sin(π/1800*t+π）+4.5 不知道需要你描述到什么地步，比如只是描述单调性呢，还是要量化，总之按着速度函数去描述肯定没有错了 d. L=0.13*5/8*π，很简单的关于弧度的定义，得出的数字精确到小数点后两位即可答案是0.26，单位是m（单位统一用国标）

There is a clock ____ the wall of the house. There is a sign hanging on the wall,which________“No Smokein There is ( )(也) a clock on the wall. There is a clock on the wall.翻译中文2 There is a clock on the wall 对a clock 提问注意加""为提问处:1.The picture "hanging" on the wall of the sitting There is a clock near the window on the wall.和There is a clo the picture is not hanging where it should on the wall 为什么从句 The picture hanging on the wall is painted by my nephew这里的挂为 The clock is on the wall(改为一般疑问句) During the 1992 campaign, a sign on the wall of cl On the wall there is a map of China.还是On the wall has a map