sin(-α)= -sinα
cos(-α) = cosα
sin(π/2-α)= cosα
cos(π/2-α) =sinα
sin(π/2+α) = cosα
cos(π/2+α)= -sinα
sin(π-α) =sinα
cos(π-α) = -cosα
sin(π+α)= -sinα
cos(π+α) =-cosα
tanA= sinA/cosA
tan（π/2＋α）＝－cotα
tan（π/2－α）＝cotα
tan（π－α）＝－tanαtan（π＋α）＝tanα
