Triangle Worksheets

**Page 1**

1.

Identify the type of ΔABC based on its angle measures.

a. | Obtuse triangle | ||

b. | Right triangle | ||

c. | Equilateral triangle | ||

d. | None of the above |

A triangle in which one of the angles is obtuse is known as an obtuse triangle.

So, ΔABC is an obtuse triangle.

Correct answer : (1)

2.

Can an equilateral triangle be a right triangle?

a. | No | ||

b. | Yes |

In a right triangle, one of the angles must be 90

So, an equilateral triangle cannot be a right triangle.

Correct answer : (1)

3.

Can a scalene triangle have an acute angle?

a. | Yes | ||

b. | No |

A scalene triangle will have an acute angle.

Correct answer : (1)

4.

Find the measure of $\angle $A, if $\angle $C = 59° and $\angle $B = 63°.

a. | 43° | ||

b. | 58° | ||

c. | 46° | ||

d. | 70° |

[Substitute

[Combine like terms.]

[Subtract 122° from both sides.]

Correct answer : (2)

5.

Name the right triangles in the rhombus.

(1) ΔABD and ΔBDC

(2)ΔAOD and ΔAOB

(3) ΔBOC and ΔDOC

(2)

(3)

a. | (1) only | ||

b. | (2) only | ||

c. | Both (1) and (2) | ||

d. | Both (2) and (3) |

In the rhombus, there are four right triangles namely ΔAOD, ΔAOB, ΔBOC and ΔDOC.

So, both (2) and (3) are correct.

Correct answer : (4)

6.

Classify the triangles in the figure based on the measure of the angles.

a. | Both are obtuse triangles | ||

b. | ΔPQR is a right triangle and ΔRST is an obtuse triangle | ||

c. | Both are right triangles | ||

d. | ΔPQR is an obtuse triangle and ΔRST is a right triangle |

ΔPQR has one obtuse angle. So, ΔPQR is an obtuse triangle.

In the figure, ΔPQR is an obtuse triangle and ΔRST is a right triangle.

Correct answer : (4)

7.

Find $\angle $A and $\angle $B for the triangle ABC, if $\angle $C = 32°.

a. | 74° | ||

b. | 94° | ||

c. | 106° | ||

d. | 84° |

So, ΔABC is isosceles and

Let

In a triangle, the sum of all the angles is equal to 180°.

[Substitute

2

[Subtract 32° from each side.]

2

[Divide each side by 2.]

Correct answer : (1)

8.

a. | 50°, 80° | ||

b. | 60°, 80° | ||

c. | 65°, 65° | ||

d. | None of the above |

A triangle with angle measures 50°, 50°, 80° and 50°, 65°, 65° forms an isosceles triangle.

Among the choices, a triangle with angle measures 50°, 60°, and 80° cannot form an isosceles triangle.

Correct answer : (2)

9.

Which of the figures is an obtuse triangle?

a. | Figure 4 | ||

b. | Figure 3 | ||

c. | Figure 2 | ||

d. | Figure 1 |

[All the angles are less than 90

Figure 2 is a right triangle.

[One angle is 90

Figure 4 is an obtuse triangle.

[One angle is greater than 90

Correct answer : (1)

10.

O is the center of the circle. Are the triangles COB and COD isosceles triangles?

a. | No | ||

b. | Yes |

CO, DO and BO are the radii of the circle.

In a circle, all radii have equal measures.

ΔCOB is an isosceles triangle.

[Since CO = BO]

Similarly, in ΔCOD, measures of segments CO and OD are equal.

ΔCOD is an isosceles triangle.

So, the triangles COB and COD are isosceles triangles.

Correct answer : (2)