sin（π/2+α）= cosα

cos（π/2+α）= -sinα

tan（π/2+α）= -cotα

cot（π/2+α）= -tanα

sin（π/2-α）= cosα

cos（π/2-α）= sinα

tan（π/2-α）= cotα

cot（π/2-α）= tanα

cos函式sin函式影象公式如下

角度a 0° 30° 45° 60° 90° 180°

1.sina 0 1/2 √2/2 √3/2 1 0

2.cosa 1 √3/2 √2/2 1/2 0 -1

3.tana 0 √3/3 1 √3 / 0

4.cota / √3 1 √3/3 0 /