Triangles WHAT IS A TRIANGLE A triangle is

Triangles

WHAT IS A TRIANGLE?

A triangle is: • A polygon • A three sided figure • A geometric shape with three angles or vertices

HOW CAN WE CLASSIFY THEM? What does “classify” mean? to sort or group together • By their angles • By their sides

Triangles Can be classified by their congruent sides

Scalene Triangle no congruent sides

Isosceles Triangle Has at least two congruent sides

Equilateral Triangle Has three congruent sides

Triangles Can be classified by the measurement of their angles

Right Triangle Has one right angle

Acute Triangle Has three acute angles

Obtuse Triangle with one obtuse angle

Triangles Cut a triangle out of the sheet of paper from Mrs. Burt

Triangles Tear off the dotted corners. Piece them together by having the corners touch. Put them together on a straight line.

Triangles The sum of the angles of a triangle is ALWAYS 180 degrees -a straight line-

Triangles To find a missing angle, add up the two angles you know

Triangles Subtract the sum from 180 and you have the missing angle

40˚ ? 70˚

Congruent Triangles

Congruent Triangles • Have the same SIZE and the same SHAPE • They may be flipped or rotated

• ABC is congruent to DEF B F E D A C

One for you • Name the congruent triangles remembering to name the angles in F order E Z means “is congruent to” D Y X ~ ZXY = FED