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Types of Triangle based on Angle

Triangles and its Properties I - Concepts

Parts of a Triangle

Angle Sum Property of a Triangle

Pythagoras Theorem

Types of Triangle based on Angle

Types of Triangle based on Side

Calculating Perimeter of Triangle

Class - 7th Foundation NTSE Subjects

Concept Explanation

Types of Triangle based on Angle

Types of Triangle based on Angle:

An acute triangle has three angles that each measure less than 90 degrees. An equilateral triangle is a triangle in which all three sides are the same length. An obtuse triangle is a triangle with one angle that is greater than 90 degrees. A right triangle is a triangle with one 90 degree angle.

The prefix “tri” means three. Triangle means three angles.

To classify a triangle according to its angles, you must look at the angles inside the triangle. Use the number of degrees in these angles to classify the triangle. Let’s look at a picture of a triangle to explain.

Look at the measure of each angle inside the triangle to figure out what kind of triangle it is. There are four types of triangles based on angle measures.

A right triangle is a triangle that has one right angle and two acute angles. One of the angles in the triangle measures $small 90^0$ and the other two angles are less than 90. Here is a picture of a right triangle.

You can see that the 90 degree angle is the one in the bottom left corner. You can even draw in the small box to identify it as a 90 degree angle. If you look at the other two angles you cans see that those angles are less than 90 degrees and are acute.

Let's look at an example of a right angle.

This triangle has one $small 90^0$ angle and two $small 45^0$ angles. Find the sum of the three angles.

$small 90^0+45^0+45^0=180^0$

The sum of the three angles of a triangle is always equal to 180âˆ˜.

In an equiangular triangle, all three of the angles are equal.

The three angles of this triangle are equal. This is an equiangular triangle.

You know that the sum of the three angles is equal to $small 180^0$ , therefore, for all three angles to be equal, each angle must be equal to $small 60^0$ .

$small 60^0+60^0+60^0=180^0$

The sum of the angles is equal to $small 180^0$ .

In an acute triangle, all three angles of the triangle are less than 90 degrees. Here is an example of an acute triangle.

All three of these angles measure less than 90 degrees.

$small 33^0+80^0+67^0$ = $small 180^0$

The sum of the angles is equal to $small 180^0$ .

An obtuse triangle has one angle that is greater than 90 and two angles that are less than 90.

$small 130^0+25^0+25^0$ = $small 180^0$

The sum of the angles is equal to $small 180^0$ .

Sample Questions

(More Questions for each concept available in Login)

Question : 1

A triangle has angle measurements of 13°, 47°, and 120°. What type of triangle is this?
A. Acute angled	B. Right angled	C. Obtuse angled	D. None of these
Right Option : C
View Explanation

Question : 2

Right-angled triangle must have ___________
A. Four right angles	B. Three right angles	C. One right angle	D. Two right angles
Right Option : C
View Explanation