A triangle is a closed planar figure with three sides and three vertices. It is one of the basic shapes in geometry. A triangle with vertices A, B, and C is denoted as △ ABC. In Euclidean geometry any three points, when non-collinear, determine a **unique triangle and a unique plane**. This article discusses triangles that result when the sides and one of the angles of a given triangle are constrained to be equal to the corresponding sides and angles of another triangle.

There are several sets of angles that can form a triangle. These include:

- Three acute angles
- An acute angle and two obtuse angles
- An **obtuse angle and two acute angles**

The three acute angles could form a triangle with the sides being the length of the side opposite to each angle in the triangle. For example, if angle A in △ ABC is an acute angle, then the sides of the resulting triangle would be the length of side a, the length of side b, and the length of side c.

An **acute angle and two obtuse angles** could form a triangle in a similar way as the three acute angles. In this case, one of the obtuse angles would be substituted for the acute angle in the previous example. For example, if angle A in △ ABC is an acute angle and angles B and C are obtuse angles, then the sides of the resulting triangle would be the length of side a, the length of side b, and the length of side **c.**

**An obtuse angle and two acute** angles could again form a triangle in a similar way as the three acute angles a**nd the acute angle and two obtuse** angles. In this case, one of the acute angles would be substituted for the obtuse angle in the previous two examples. For example, if angle A in △ ABC is an obtuse angle and angles B and C are acute angles, then the sides of the resulting triangle would be the length of side a, the length of side b, and the length of side c.

There are other sets of angles that could form a triangle, but these are the most common and easily remembered.

## What is the sum of the angles in a triangle?

There are three angles in a triangle, and the sum of these angles is always 180 degrees. This is because a triangle is a **two-dimensional shape with three straight sides**, and the three angles inside always add up to 180 degrees. This is true no matter what size or shape the triangle is.

## What is the largest angle in a triangle?

A triangle is a three-sided polygon. The largest angle in a triangle is the **angle opposite the longest side** of the triangle. The longest side of a triangle is the hypotenuse. The hypotenuse is the side of a right triangle that is opposite the right angle. The other two sides of a right triangle are the shorter sides. The length of the hypotenuse is equal to the length of the longest side of the triangle.

## What is the smallest angle in a triangle?

A triangle is a polygon with three sides and three vertices. The smallest angle in a triangle is the angle between the two shortest sides. This angle is also known as the vertex angle. The vertex angle is the angle between the two sides of the triangle that intersect at the vertex. The vertex angle is the angle between the two lines that intersect at the vertex.

## What is the difference between the largest and smallest angles in a triangle?

There are a few different ways to think about the difference between the largest and smallest angles in a triangle. One way to think about it is in terms of the sides of the triangle. The longest side of the triangle will always be opposite the largest angle, and the shortest side of the triangle will be opposite the smallest angle. Another way to think about it is in terms of the angles themselves. The largest angle in a triangle is always going to be greater than the smallest angle. The smallest angle will be less than or equal to half of the largest angle.

## Can two angles in a triangle be equal?

Can two angles in a triangle be equal? This is a question that has been debated by mathematicians for centuries. Euclid's Elements, one of the most influential works in mathematics, states in Proposition I.4 that "in every triangle, the sum of the two shorter sides is greater than the longer side." This proposition is often referred to as the Triangle Inequality. From this Proposition, it follows that if two angles in a triangle are equal, then the third angle must be greater than the other two.

However, there are some mathematicians who believe that the Triangle Inequality does not necessarily hold for all triangles. They believe that there could be a triangle in which two angles are equal and the third angle is less than the other two. While this may seem like a contradiction, it is actually possible to create such a triangle.

To do this, we must start with a triangle that does satisfy the Triangle Inequality. We can then bisect one of the angles, creating two new angles that are each less than the original angle. We can then bisect one of the new angles, creating two even smaller angles. Continuing this process, we can create two angles that are arbitrarily close to being equal. The third angle in our triangle will then be less than the other two angles, since it is the difference between the two bisected angles.

So, there is a way to create a triangle in which two angles are equal and the third angle is less than the other two. However, it is important to note that this is not a "real" triangle in the traditional sense. It is a so-called "degenerate" triangle, which means that it is not a true geometric figure. In other words, while it is possible to create a triangle in which two angles are equal, it is not possible to create such a triangle in the real world.

## Can two angles in a triangle be complementary?

Can two angles in a triangle be complementary? This is a **commonly asked question among geometry students** and the answer is yes, but there are a few conditions that must be met in order for this to be possible. First, the triangle must be a right triangle, meaning that one of the angles must be a 90 degree angle. Secondly, the other two angles must add up to 90 degrees as well. If these two conditions are met, then the two angles are complementary.

A right triangle is a triangle in which one of the angles is a 90 degree angle. The other two angles of a right triangle are called the acute angles. Acute angles are angles that are less than 90 degrees. The two acute angles in a right triangle must add up to 90 degrees in order for the triangle to be a right triangle.

So, if a triangle is a right triangle and the two **acute angles add up to 90 degrees**, then the two angles are complementary.

## Can two angles in a triangle be supplementary?

Two angles in a triangle can be supplementary if the sum of their measures is equal to 180 degrees. Angles that are supplementary have a non-acute angle between them, which means that their measures do not add up to 90 degrees. In a right triangle, the two angles that are supplementary to the right angle are the other two angles in the triangle.

## What is the relationship between the angles of a triangle and the sides of a triangle?

The most basic and well-known fact about triangles is that the sum of the angles of a triangle is always 180 degrees. This is often used as a definition of a triangle, and it is certainly a necessary condition for a figure to be a triangle. But it is not, by itself, sufficient.

There are other shapes that have three angles that sum to 180 degrees, but are not triangles. The most obvious are the shapes that result from taking a triangle and folding it along one or more of its sides:

It is clear that the angles of the folded shapes are the same as the angles of the triangle, but the sides are not. So the converse of the statement "the sum of the angles of a triangle is 180 degrees" is not true.

Another way to see that the sum of the angles of a triangle is not, by itself, sufficient to define a triangle is to consider a "triangle" with sides of zero length:

Here the **angles sum to 180 degrees**, but there is no triangle.

So we need a definition of a triangle that is both necessary and sufficient. The definition most people learn is "a triangle is a three-sided polygon". This is both necessary and sufficient: it is necessary because a three-sided polygon is, by definition, a figure with three sides; and it is sufficient because any figure that has three sides is necessarily a triangle (since the sum of the angles must be 180 degrees).

But there is another definition that is sometimes used, and that is "a triangle is a figure with three sides of non-zero length". This is also both necessary and sufficient: it is necessary because a triangle, by definition, has three sides; and it is sufficient because any figure that has three sides of non-zero length must be a triangle (since the sum of the angles must be 180 degrees).

So which of these two definitions should we use? It doesn't really matter, as long as we are consistent. In this article we will use the first definition, "a triangle is a three-sided polygon".

With this definition, it is clear that the relationship between the angles of a triangle and the sides of a triangle is that the sides of a triangle are the sides of a three-sided polygon.

## If two angles in a triangle are equal, what can you say about the third angle?

If two angles in a triangle are equal, then the third angle must be equal to the other two angles. This is because the sum of the angles in a triangle is always 180 degrees. Therefore, if two angles in a triangle are 90 degrees, the third angle must also be 90 degrees.

## Frequently Asked Questions

### How many kinds of triangles can be formed according the angles?

There are only six possible triangles that can be formed based on angles. They are: right triangles, obtuse triangles, acute triangles, straight lines, congruentagons and similar polygons.

### What is the sum of all angles of a triangle?

The sum of all angles of a triangle is 180°.

### What do all angles add up to in an isosceles triangle?

180°

### What are the different types of triangles?

There are three types of triangles: right triangle, obtuse triangle, and isosceles triangle.

### Do all triangles have the same angles?

No, all triangles do not have the same angles. Two triangles have the same angles if and only if they have the same lengths of sides.