cos三角函数表：cos0°=1、cos15°=（√6+√2）/4、cos30°=√3/2、cos45°=√2/2、cos60°=1/2、cos75°=sin15°、cos90°=0。
三角函数cos公式
cos(-a) = cos(a
sin(π/2 - a) = cos(a)
cos(π/2 - a) = sin(a)
sin(π/2 + a) = cos(a)
cos(π/2 + a) = - sin(a)
cos(π - a) = - cos(a)
cos(π + a) = - cos(a)
sin(a + b) = sin(a)cos(b) + cos(α)sin(b)
cos(a + b) = cos(a)cos(b) - sin(a)sin(b)
sin(a - b) = sin(a)cos(b) - cos(a)sin(b)
cos(a - b) = cos(a)cos(b) + sin(a)sin(b)
sin(a) + sin(b) = 2sin[(a + b)/2]cos[(a - b)/2]
sin(a) - sin(b) = 2sin[(a - b)/2]cos[(a + b)/2]