............ is credited with giving the first known proof.

Solve the following question using appropriate Euclid's axiom:
Two salesmen make equal sales during the month of August. In September,each salesman doubles his sale of the month of August. Compare their sales in September.

The edges of a surface are ............

Give a definition for the term 'line segment'. Are there other terms that need to be defined first? What are they,and how might you define them?

The Greeks emphasized on:

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