“That is a term denoting a figure of three sides, and angles. I dare say Tom can describe the several kinds of triangles.”
Tom accordingly took the pencil, and drew a set of figures, of which the annexed are faithful copies.
“A,” said he, “is an Equi-lateral triangle; its three sides being all equal. B is a Right-angled triangle, having one right angle. C represents an Obtuse-angled triangle, it having one obtuse angle. An Acute-angled triangle is one in which all the three angles are acute, as represented in figure A.”
“As you have succeeded so well in your explanation of a triangle, let us see whether you can describe the nature of a circle.”
“It is a round line, every part of which is equally distant from the centre.”
“And which round line,” said Mr. Seymour, “is frequently called the circumference. What is the diameter?”
“A straight line drawn through the centre, and terminating in the circumference on both sides.”
“And an arc?” said Mr. Seymour.
“Any portion of the circumference.”