Triangles

Triangles

There are many terms and Theroms about triangles. Here are a few of each.

BY THEIR SIDES

	Scalene - no congruent sides.
	Isosceles - two congruent sides. (DF = FE)
	Equilateral - three congruent sides.

BY THEIR ANGLES

	Acute - all angles measure less than 90^º.
	Right - one angle measures exactly 90^º.
	Obtuse - one angle measures more than 90^º.
	Equiangular - all angles measure the same. (60^º) This is the same as the equilateral triangle.

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If a straight line is drawn parallel to one side of a triangle, the other two sides are divided proportionally. (theorem j)

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If two triangles are equiangular their corresponding sides are proportional. (theorem k)

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If two triangles have one equal angle and the sides about these equal angles are proportional, then the triangles are similar. (theorem l)

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If a triangle is drawn from the right angle of a right angled triangle to the hypotenuse, then the triangles on each side of of the perpendicular are similar to the whole triangle and to one another. (theorem m)

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The internal bisector of an angle of a triangle divides the opposite side in the ratio of the sides containing the angle. (theorem n)

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