16. Give one enunciation that will include Propositions xi., xii. of Book III.
17. What Proposition is this a limiting case of?
18. Explain the extended meaning of the word angle.
19. What is Euclid’s limit of an angle?
20. State the relations between Propositions xvi., xviii., xix.
21. What Propositions are these limiting cases of?
22. How many common tangents can two circles have?
23. What is the magnitude of the rectangle of the segments of a chord drawn through a point 3.65 metres distant from the centre of a circle whose radius is 4.25 metres?
24. The radii of two circles are 4.25 and 1.75 feet respectively, and the distance between their centres 6.5 feet; find the lengths of their direct and their transverse common tangents.
25. If a point be h feet outside the circumference of a circle whose diameter is 7920 miles, prove that the length of the tangent drawn from it to the circle is