Step 3. From B swing an arc equal to BP and from
1. The altitude of a triangle is a line drawn from the
this intersection with the circle, draw the
vertex, perpendicular to the base.
diameter, thus dividing circle O into 8 equal
2. The median of a triangle is a line drawn from the
vertex to the midpoint of the base.
A triangle is a plane shape having 3 sides. Its name
is derived from its three (tri) angles.
Other facts help define a triangle.
1. The sum of the angles in any triangle equals
2. A triangle is the only plane shape which maybe
defined in terms of its sides only; in all others
one or more angles must be stated.
Types of Triangles
There are four kinds of triangles. They are classified
according to the size of their sides and angles as follows:
1. Equilateral-all sides are equal-all angles are
equal-all angles are 60°
2. Isoscelestwo sides equal-two angles equal
3. Scaleneall sides unequal-all angles unequal
4. Rightone right angle
Altitudes and Medians
The altitude and median of a triangle are not the
same; the difference is pointed out in the following
Construction of Triangles
There are many ways to construct a triangle, de-
pending upon what measurements are known to you.
The following examples will assist you. Select the ap-
propriate method according to the information given
about the triangle.
1. A triangle may be constructed if the lengths of
three sides are known.
Construct a triangle.
Three sides of a triangle: 2, 1, 1 1/2.