Triangles

Triangles Three sides Three angles Measures a total of 180°

Triangles Equilateral Isosceles Scalene

Triangles Equilateral Three equal sides Three equal angles, always 60°

Triangles Isosceles Two equal sides Two equal angles

Triangles Scalene No equal sides No equal angles

Which is which?

Practice Work on the following handout

Triangles Right Obtuse Acute

Triangles Right Triangle A triangle with a right angle

Triangles Right Triangle Isosceles Right One right angle Two other equal angles always of 45° Two equal sides Scalene Right Two other unequal angles No equal sides 60° 30°

Triangles Acute Triangle A triangle with all angles less than 90°

Triangles Obtuse Triangle A triangle with one obtuse angle

Which is which?

Triangle Properties The sum of the interior angles is always 180 degrees

Triangle Properties If you need to find the missing angle inside a triangle: Find the sum of the known angles Subtract this sum from 180 70° + 50° 120° 180°-120° 60° a=60°

Triangle Properties

Practice Work on the following handout

Triangle Properties Interior and Exterior Angles are supplementary

Triangle Properties Interior and Exterior Angles are supplementary

Triangle Properties Interior and Exterior Angles are supplementary

Practice Work on the following handout

Triangle Properties The longest side of a triangle is opposite the largest angle 30° 100° 50°

Which is the longest?

Practice Work on the following handout