代数几何:三角函数

一, 三角函数                          

   正弦sin(a) = b / c

   余弦cos(a)  = a / c

   tan(a) = b / a

   csc(a) = 1 / sin(a) = c / b

   sec(a) = 1 / cos(a) = c / a

    cot(a) = 1 / tan(a) = a / b

                                 常用的三角函数函数值表

a (Degrees)

a (Radians)

sin a cos a tan a
0 0 0 1 0
30 PI / 6 0.5 0.8660 0.5774
45 PI / 4 0.7071 0.7071 1
60 PI / 3 0.8660 0.5 1.7321
90 PI / 2 1 0 -----
120 2*PI/3 0.8660 -0.5 -1.7321
180 PI 0 -1 0
270 3*PI/2 -1 0 -----
360 0 0 1 0

  正弦函数曲线

  余弦函数曲线

  

二, 三角代数                          

     由单位圆 x2 + y2 = 1来推导

  sin2a + cos2a = 1

  sin(-a) = -sin(a)

  cos(-a) = cos(a)

  tan(-a) = -tan(a)

 

  sin(a1 + a2) = sin(a1) * cos(a2) + cos(a1) * sin(a2)

  sin(a1 - a2) = sin(a1) * cos(a2) - cos(a1) * sin(a2)

 

   cos(a1 + a2) = cos(a1) * cos(a2) - sin(a1) * sin(a2)

   cos(a1 - a2) = cos(a1) * cos(a2) + sin(a1) * sin(a2)

 

原文:http://www.cnblogs.com/HelloCG/

posted @ 2015-02-13 06:20  ^_^肥仔John  阅读(1903)  评论(0编辑  收藏  举报