# DEF Definitions of Conics

- Author:
- Wang Muran

Any conic section can be defined as the locus of points whose distances to a point (the

**focus**) and a line (the**directrix**) are in a constant ratio (the**eccentricity**). In this activity, we shall explore how**eccentricity**affects the shape of the conics.## Instructions:

1. Drag to set the fixed point

*F*; drag the red dot to set the fixed line*d*. 2. Use the slider to adjust the eccentricity*e*. 3. Click the checkbox to construct the locus of the variable point*P*satisfying**. 4. Click the 'Erase' button before constructing a new locus.***PF*/*Pd*=*e*## Questions:

1. How does the eccentricity

*e*affect the locus of*P*? 2. Predict the locus when*e*= 0.