Grade 6 - Mathematics 9.19 Classifying Triangles by Angles

Classification of triangles based on angles

Acute angled triangle:

If all the angles of a triangle are acute angles, then it is called an acute angled triangle.

Right angled triangle:

A triangle in which one of the angles is a right angle is called a right angled triangle.

In a right angled triangle, the side opposite to the right angle is called its hypotenuse.

Obtuse angled triangle:

A triangle containing an obtuse angle is called an obtuse angled triangle.

Directions: Read the above properties of triangles and answer the following questions:

Illustrate each of the above properties by drawing a triangle.

Write in your own words, how to classify triangles according to their angles.

Q 1: The side opposite to the right angle in a right angled triangle is called the ________ of the triangle. Answer:

Q 2: A (an) ________ angled triangle has its angle measures as 100 degrees, 60 degrees and 20 degrees. Answer:

Q 3: If, in a triangle, 70 degrees, 55 degrees and 55 degrees represents its angles, then the triangle is a (an) ________. Right angled isosceles triangle Acute angled isosceles triangle Obtuse angled isosceles triangle

Q 4: The angles 90 degrees, 45 degrees and 45 degrees represents a (an) ________ triangle. Obtuse angled scalene Acute angled isosceles Right angled isosceles

Q 5: The angles 90 degrees, 30 degrees and 60 degrees represents an obtuse angled triangle. False True

Q 6: If the angles of a triangle are given by 100 degrees, 30 degrees and 50 degrees, then the triangle is an right angled triangle. True False

Q 7: The angles 30 degrees, 60 degrees and 90 degrees represents a (an) ________ angled triangle. Answer:

Q 8: The angles 70 degrees, 80 degrees and 30 degrees represents the angles of an acute angled triangle. True False

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