The trigonometric ratios sine, cosine and tangent are used to calculate angles and sides in right angled triangles. We are now going to extend trigonometry beyond right angled triangles and use it ...

The graph of y = tan θ As the point P moves anticlockwise round the circle, the values of cos θ and sin θ change, therefore the value of tan θ will change. This graph has a period of 180°.