Classifying Triangles

There are Two Ways to Classify Triangles By Their Sides By Their Angles

Scalene Isosceles Equilateral If we are classifying triangles by their sides we can use the following terminology: Scalene Isosceles Equilateral

Scalene Triangles No sides are the same length

Isosceles Triangles Two sides are the same length

Equilateral Triangles All sides and angles are the same length and size. Equilateral Triangles

Classifying Triangles By Their Angles Acute Right Obtuse

Acute Triangles Acute triangles have three acute angles This means that all angles range between 1 and 89 degrees!

Right Angled Triangles Right triangles have one right angle… Who would have guessed?!? This means that the triangle has at least one 90 degree angle. This is often shown by having a little square in the corner.

Obtuse Triangles Obtuse triangles have one obtuse angle This means that there is one angle in the triangle that ranges from 91 to 179 degrees!

Classify this triangle. Right Scalene

Classify this triangle. Obtuse Isosceles

Classify this triangle. Acute Scalene

Classify this triangle. Acute Isosceles

Classify this triangle. Obtuse Scalene

Classify this triangle. Right Isosceles

The sum of the measures of any triangle is 180°. Triangle Degrees The sum of the measures of any triangle is 180°. x What is the measure of x? 60° 50°

Triangle Degrees The sum of the measures of any triangle is 180°. 70° What is the measure of x? x

Angles in a triangle sum to 180° 70° 50° x x = 60° Angles in a triangle sum to 180° 50° x x = 50° Base angles of an isosceles triangle are equal x x = 60° Each angle in an equilateral triangle is 60°

Angles in a quadrilateral sum to 360° 50° 70° x x = 120° Exterior angle of a triangle equals the sum of the 2 interior opposite angles 120° 100° 80° x x = 60° Angles in a quadrilateral sum to 360°

Types of Quadrilaterals □ I □ » I I II II ^ ^ » I I Parallelogram □ □ I Rectangle Rhombus □ I □ » I I I I II □ □ II I » Square Trapezium Kite