If two circles are equal, then their radii are equal.

Is the statement true or false? Give reasons.

In the following figure, if $\mathrm{A}\mathrm{B}=\mathrm{P}\mathrm{Q}$ and $\mathrm{P}\mathrm{Q}=\mathrm{X}\mathrm{Y},$ then $\mathrm{A}\mathrm{B}=\mathrm{X}\mathrm{Y}$.

Define radius of a circle. Are there other terms that need to be defined first? What are they, and how might you define them?

Consider two ‘postulates' given below:

(i) Given any two distinct point $\mathrm{A}$ and $\mathrm{B}$, there exists a third point $\mathrm{C}$ which is in between $\mathrm{A}$ and $\mathrm{B}$.

(ii) There exist at least three points that are not on the same line.

Do these postulates contain any undefined terms? Are these postulates consistent? Do they follow from Euclid postulates? Explain.