In mathematics, the sine is a trigonometric function of an angle. The sine of an acute angle is defined in the context of a right triangle.
for the specified angle, it is the ratio of the length of the side that is opposite that angle to the length of the longest side of the triangle (the hypotenuse).
in mathematics: 在数学上
trigonometric function 三角函数
acute angle 锐角
be defined in the context of ： 以...形式来定义
right triangle： 直角三角形
for the specified angle: 就某个角（应该是锐角）而言
重点句子分析:
it is the ratio of the length of the side that is opposite that angle to the length of the longest side of the triangle
it is句型: 科技英文中，it is/there be/被动语句/定语从句满天飞.
ratio常用的表示: the ratio of sth1 to sth2，表示 sth1 和 sth2之间的比值
sth1: the length of the side that is opposite that angle
可以分为两部分来看，既:
the length of the side 边的长度
that is opposite(对面) that angle其中that is 第一个that是定语从句开始，修饰side。 第二个that是指代 the specified anglet. 讲了这么多，中文就用对边来表示sth2: the length of the longest side of the triangle(三角形最长的边),中文就用斜边来表示
所以: sinA = 对边 / 斜边
专门买的数位板，训练一段时间，万一在拍摄视频分享时需要画画草图，列列公式之类的话，数位板还是蛮有用的。
