tan θ = sin θ cos 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. The graph has a period of 180°.

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°.