Classifying Triangles ...

Classifying Triangles

www.pleasanton.k12.ca.us/.../Powerpoints/4.1_Triangles_and_Angle...

Equilateral

3 congruent sides

Isosceles

At least 2 congruent sides

Scalene

No congruent sides

Equilangular

3 congruent angles

Acute

3 acute angles

Obtuse

1 obtuse angle

Right

1 right angle

Vertex: the point where two sides of a triangle meet

Adjacent Sides: two sides of a triangle sharing a common vertex Hypotenuse: side of the triangle across from the right angle

Legs: sides of the right triangle that form the right angle

Base: the non-congruent sides of an isosceles triangle

Label the following on the right

triangle: Vertices Hypotenuse Legs

Vertex

VertexVertex

Hypotenuse

Leg

Leg

Label the following on the isosceles

triangle:

Base Congruent adjacent

sides Legs

m<1 = m<A + m<B

Adjacent side

Base

Adjacent Side

Leg Leg

Interior Angles: angles inside the triangle

(angles A, B, and C)

A

B

C

1

2

3

Exterior Angles: angles adjacent to the interior angles

(angles 1, 2, and 3)

The sum of the measures of the interior angles of a triangle is 180o.

A

B

C

<A + <B + <C = 180o

The measure of an exterior angle of a triangle is equal to the sum of the measures of two nonadjacent interior angles.

A

B

1

m<1 = m <A + m <B

The acute angles of a right triangle are complementary. B

A

m<A + m<B = 90o

www.pleasanton.k12.ca.us/.../Powerpoints/4.1_Triangles_and_Angle...