© M. Tallman

© M. Tallman

All three sides are congruent.

4 inches

4 inches

4 inches

All three angles are also congruent, 60°.

60° 60°

60°

Note: an equilateral triangle will always have three 60° angles, no matter what the size of the triangle.

© M. Tallman

Two sides are congruent.

4 inches

3 inches

4 inches

Two angles are congruent.

70° 70°

40°

One side has a different length.

One angle is different.

Click here for a helpful

trick.

© M. Tallman

All sides are different lengths.

5.5 inches

7 inches

3 inches

All angles are different.

50° 20°

110°

© M. Tallman

Has one right angle.

90°

Note: It is not possible for a triangle to have more than one right angle.

© M. Tallman

All three angles are acute (less than 90°).

50° 60°

70°

© M. Tallman

One angle is obtuse (greater than 90 °) .

110°

Note: It is not possible for a triangle to have more than one obtuse angle.

© M. Tallman

Equilateral, Isosceles, Scalene, Right, Acute, Obtuse.

X°Z°

Y°

a un

its

b units

c units

© M. Tallman

Equilateral, Isosceles, Scalene, Right, Acute, Obtuse.

90°X°

Y°a u

nit

s

b units

c units

© M. Tallman

Equilateral, Isosceles, Scalene, Right, Acute, Obtuse.

X°a

units

a units

a units

X° X°

© M. Tallman

Equilateral, Isosceles, Scalene, Right, Acute, Obtuse.

X°b u

nits b

units

Y° Y°

a units

© M. Tallman

Equilateral, Isosceles, Scalene, Right, Acute, Obtuse.

X°a u

nit

s

a units

X°

b units

© M. Tallman

Equilateral, Isosceles, Scalene, Right, Acute, Obtuse.

Y°

a units

b units

Z° X°

c units

© M. Tallman

Equilateral, Isosceles, Scalene, Right, Acute, Obtuse.

X°

a units

b units

Y°a units

X°

© M. Tallman

Obtuse or Scalene

50°20°

110°

20° 50°

110°

Although there are many different types of triangles, the sum of their angles will always equal

180°.

50°110°

20°

20° + 110° + 50° = 180°

© M. Tallman

60° 60°

60°

Equilateral or Acute

60°

60°60°

Although there are many different types of triangles, the sum of their angles will always equal

180°.

60° + 60° + 60° = 180°

60°60°

60°

© M. Tallman

35°

55°

Right or Scalene

90°

55°

Although there are many different types of triangles, the sum of their angles will always equal

180°.

35° + 90° + 55° = 180°

90° 35°

90°35° 55°

© M. Tallman

70° 70°

40°

isosceles 70°

40°

70°

Although there are many different types of triangles, the sum of their angles will always equal

180°.

40° + 70° + 70° = 180°

70°40° 70°

© M. Tallman

120°

Find the missing angle. Then classify the triangle.

60° + 60° =120°

60° ?

60°

60°

180° - =60°

© M. Tallman

80°60° + 20° = 80°

60°

180° - = 100°

100°?

20°

Find the missing angle. Then classify the triangle

© M. Tallman

135°90° + 45° =135° 180° - =45°

45°

?45°

Find the missing angle. Then classify the triangle

© M. Tallman

110°65° + 45° =110°

70°

180° - = 70°

45°?

65°

Find the missing angle. Then classify the triangle

© M. Tallman

160°115°+ 45° =160°

45°

180° - = 20°

115°

?20°

Find the missing angle. Then classify the triangle

© M. Tallman

140°70° + 70° =140°

70°

180° - = 40°

40°?

70°

Find the missing angle. Then classify the triangle

© M. Tallman

150°90° + 60° =150° 180° - =30°

60°

?30°

Find the missing angle. Then classify the triangle

© M. Tallman

130°90° + 40° =130° 180° - =50°

40°

?50°

Find the missing angle. Then classify the triangle

© M. Tallman

130°110°+ 20° =130°

20°

180° - = 50°

110°

?50°

Find the missing angle. Then classify the triangle

© M. Tallman

155°

Find the missing angle. Then classify the triangle

25° +130°=155°

25° ?

130°

25°

180° - =25°

© M. Tallman

Isosceles TrianglesosCan’t remember what an isosceles triangle is?

Try using this little trick!

The “sos” in isosceles can stand for same-outcast-same.

sam

e

same

outcast

O

S S

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