BOOK I. DEFINITIONS.
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XXIV.
A triangle whose three sides are equal, is said to be equilateral.
XXV.
A triangle which has only two sides equal is called an isosceles triangle.
XXVI.
A scalene triangle is one which has no two sides equal.
XXVII.
A right angled triangle is that which has a right angle.
XXVIII.
An obtuse angled triangle is that which has an obtuse angle.
XXIX.
An acute angled triangle is that which has three acute angles.
XXX.
Of four-sided figures, a square is that which has all its sides equal, and all its angles right angles.
XXXI.
A rhombus is that which has all its sides equal, but its angles are not right angles.
XXXII.
An oblong is that which has all its angles right angles, but has not all its sides equal.
