The largest angle in a triangle is an obtuse angle, which is an obtuse triangle. Is that right?

Right. There is a triangle with obtuse angles called obtuse triangles.

In a triangle, there can only be at most one obtuse angle, so if the largest angle is obtuse, then it is an obtuse triangle.

That's right. Judging the type of triangle, mainly according to the size of the inner angle of the triangle, if the three inner angles of the triangle are less than 90 degrees, it is called an acute triangle, when one of them is called 90 degrees, it is called a right triangle; If one of the angles is greater than 90 degrees, that is, an obtuse angle, it is called an obtuse triangle.

Right. According to the sum theorem of the inner angles of a triangle, the sum of the three angles of a triangle is 180°, and if one of the angles is obtuse, then the triangle must be an obtuse triangle.

Yes, the definition and judgment of an obtuse triangle:

That's right. The largest angle in a triangle is an obtuse angle, and this triangle is an obtuse triangle.

A triangle with one angle that is obtuse is an obtuse triangle, a triangle with one angle that is a right angle is a right triangle, and a triangle with three angles that are all acute angles is an acute triangle. The largest angle in a triangle is an obtuse angle, and it is an obtuse triangle, and this statement is true.

Yes. Because it is impossible for two or more numbers to be obtuse in any one triangle, there is only one obtuse angle in an obtuse triangle. As long as there is an obtuse angle, the triangle is an obtuse triangle.

Yes, as long as one of the corners in the triangle is obtuse, then this triangle is an obtuse triangle. This is junior high school math knowledge, and you can consult your junior high school math teacher for the knowledge of triangles.

That's right. A triangle with one angle that is obtuse is an obtuse triangle (apparently only one corner can be obtuse).

That's right, in a triangle, one with a right angle is a right triangle, one with an obtuse angle is an obtuse triangle, and one with three acute angles is an acute triangle.

The largest angle in a triangle is an obtuse angle, which is an obtuse triangle. Right.

Analysis: A triangle with an obtuse angle is an obtuse triangle.

In a triangle with one obtuse angle, the remaining two angles are acute angles.

Acute triangle: Because the three inner angles are all acute angles, the outer angles correspondingly have three obtuse angles;

Obtuse triangle: Because one of the three inner angles is obtuse and the remaining two are acute, the corresponding outer angles have two obtuse angles.

Right triangle: Because one of the three inner angles is a right angle and the remaining two are acute angles, the corresponding outer angles have 2 obtuse angles.

To sum up: there are at least 2 obtuse angles in the outer corners of the triangle. ( Included in obtuse triangles and right triangles).

Acute triangle: because the three inner angles are all acute angles, the outer angles correspondingly have 6 obtuse angles;

Obtuse triangle: Because one of the three inner angles is obtuse and the remaining two are acute, the corresponding outer angles have 4 obtuse angles.

Right triangle: Because one of the three inner angles is a right angle and the remaining two are acute, the corresponding outer angles have 4 obtuse angles.

If there is a triangle with an obtuse angle, it must be an obtuse angle, and the triangle is incorrect.

A triangle with an obtuse angle is not necessarily an obtuse triangle. If a triangle has only one obtuse angle, then it is called an obtuse triangle; If a triangle has three obtuse angles, then it is called an obtuse triangle. Therefore, a triangle with obtuse angles is likely to be an acute triangle, as long as the sum of the remaining two angles is less than 90 degrees.

According to the sum theorem of the inner angles of a triangle, the sum of the three interior angles of a triangle is equal to 180 degrees. Therefore, if one of the corners in a triangle is obtuse, then the sum of the remaining two angles must be greater than 90 degrees to satisfy the sum of the internal angles theorem. If the sum of the remaining two angles is less than or equal to 90 degrees, then the triangle cannot exist, because the sum of the two acute angles is 0 degrees, and it is impossible to reach 180 degrees with an obtuse angle.

Thus, a triangle with an obtuse angle can be an acute triangle and not necessarily an obtuse triangle.

For example, the three angles of a triangle are 40 degrees, 80 degrees and 60 degrees. 80 degrees are obtuse angles, and 40 degrees and 60 degrees are acute angles. The sum of the two acute angles of this triangle is 100 degrees, which is greater than 90 degrees, so this triangle is not an obtuse triangle, but a triangle with one obtuse angle and two acute angles.

Therefore, a triangle is obtuse only if all three corners are obtuse, otherwise it is a triangle with one or two acute angles.

A triangle with an obtuse angle is not necessarily an obtuse triangle, and if one of the corners in a triangle is obtuse, then the sum of the remaining two angles must be greater than 90 degrees in order to satisfy the sum of the internal angles theorem. If the sum of the two angles of the rest of the state is less than or equal to 90 degrees, then the triangle cannot exist.

The use of triangles.

1. Geometry: In geometry, triangles are one of the simplest polygons, so many mathematical theories and formulas are developed on the basis of triangles.

2. Physics: The translational and rotational motion of the particle can be regarded as a triangle and then the trigonometric function (such as sine, cosine, tangent, etc.) can be used to describe its trajectory.

3. Angle measurement: Angle is a basic property of a triangle, so the size of the angle can be calculated by trigonometric functions.

4. Engineering: For example, in architectural design and civil engineering, the structure and safety of a building are determined by calculating the angle and side length of a triangle.

From the figure, it can only be seen that one corner of the hand is an acute angle, and the other two corners can be completely destroyed as an acute angle, or there is an obtuse angle of the fiber cover, or there is a right angle;

So all three scenarios are possible

Therefore, d

In a triangle, there is an angle that is obtuse, which is called an obtuse triangle closed branch. It is also possible that there is a sedan with a right angle, called a right triangle.

Any triangle has at least two acute angles, and friends can only have at most one right or obtuse angle. If a triangle has all three angles of acute angles, it is called an acute triangle. Acute triangles and obtuse triangles are collectively referred to as oblique triangles.

This is a real imitation of Bi.

For example, in the known δabc, a 90°Assuming that at least one of the two angles is greater than or equal to 90°, such as b 90°, then it must be.

a+∠b+∠c＞180°

This contradicts the triangular three-inner corner skin with a stupidity equal to 180°.

So the other two angles must be acute angles.

The above is a counter-argument).

Because the two outer angles of the triangle are obtuse, the two inner angles are acute angles, less than 90 degrees, and the sum of the inner angles of the triangle is equal to 180 degrees.

Therefore, the shape of this triangular chaxun shape is an obtuse triangle.

Angles greater than 90° are called obtuse angles.

According to the sum theorem of the inner angles of the triangle: the sum of the internal angles of the triangle is 180°If a triangle has two obtuse angles, the sum of the two angles is already greater than 180°, which does not conform to the sum theorem of the inner angles of the triangle, so a triangle has only one obtuse angle at most.

In the same way, a triangle has only one right angle at most.

If there are two inner angles, it is greater than 180 degrees.

First of all, it may be an acute triangle, a right triangle, an isosceles triangle, or an equilateral triangle.

It can be judged according to the characteristics of the triangle:

Acute triangle: The three corners are all acute angles, and there are no obtuse angles to match the topic.

Right triangle: There is an angle that is a right angle, because the sum of the inner angles of the triangle is 180°, so an angle is a right angle (90°), then there can be no other obtuse angles, which is in line with the topic.

Obtuse triangle: There is an angle that is obtuse and does not conform to the exclusion of the topic.

The above two are classified according to the angle, and can also be classified according to the edge:

Isosceles triangle: There are two sides that are equal, there is no provision for angles, so it is possible.

Equilateral triangle: A triangle with three equal sides, all three angles are 60°, which is in line with the title.

Arbitrary Triangle: A triangle that is not isosceles or unequal. However, people generally assume that any triangle is a triangle, and I won't mention it here.

There are the following solutions to this type of problem:

1. Find out the data and requirements that are already in the question (in this question: triangles, no obtuse angles).

3. Find the idea that fits the question, (in this question: find all the possibilities of triangles without obtuse angles).

4. Improve the idea and solve it. (Solution: Acute triangle, right triangle, isosceles triangle, or equilateral triangle).

In short, as long as the relevant knowledge points are thoroughly understood, skillfully used, and can be used anytime and anywhere, then all problems can be solved.

There are many criteria for classifying triangles, one of which is based on angles. This problem is based on the premise that according to the classification standard of triangles, there is no obtuse angle to explain that it is divided according to the angle, so it may be a right triangle and an acute triangle, and it can be seen from the following analysis: this triangle is either a right triangle or an acute triangle; Here's why:

If a triangle has an angle that is at right angles, then the triangle is a right triangle; A triangle with an angle greater than 90° is an obtuse triangle; Three angles less than 90° are acute triangles;

Take 90° as the standard: angles less than 90° are called acute angles, angles equal to 90° are called right angles, and angles greater than 90° are called obtuse angles;

The condition in the problem is given that "a triangle has no obtuse angles", which means that the angles in this triangle are only right or acute;

To sum up, this triangle is either a right triangle or an acute triangle;

Do you think this is not high quality? Want to write**? Huh).

The triangle is divided into:

A triangle with three acute angles is called an acute triangle;

A triangle with a corner that is a right angle is called a right triangle;

There is a triangle with obtuse angles called obtuse triangles.

There are two triangles with equal sides, called isosceles triangles;

A triangle in which all three sides are equal is called an equilateral triangle.

An obtuse angle is an angle greater than 90°, if the triangle does not have an obtuse angle, that is, all three angles are less than or equal to 90°, the triangle may be a right triangle, an isosceles triangle, an equilateral triangle, and an acute triangle.

Solution: A triangle does not have obtuse angles, it may be an acute triangle, because a triangle with three angles that are all acute angles is an acute triangle; A triangle does not have obtuse angles, and it can also be a right triangle because a triangle with a right angle is a right triangle.

The way to classify triangles by angle is: a triangle with three acute angles is an acute triangle; A triangle with an angle that is a right angle is a right triangle; A triangle with an angle that is obtuse is an obtuse triangle. ）

The concept of obtuse angle is greater than 90 degrees and less than 180 degrees, according to the meaning of the title, this triangle does not have an obtuse angle, that is to say, its three internal angles are less than 90 degrees or at most one internal angle is equal to 90 degrees. So it may be an acute triangle or a right triangle.

Right or acute triangles.

The reason is as follows, there are 3 types of triangles, right angles, acute angles, and obtuse angles. A triangle with right angles is a right angle, an obtuse triangle with an obtuse angle, and an acute triangle with neither right angles nor obtuse angles.

Because a triangle does not have obtuse angles, it is either a right triangle or an acute triangle.

It is a right triangle or an acute triangle. Because the problem suggests that a triangle has no obtuse angles, it can be shown that each of the triangle's internal angles is less than or equal to 90 degrees. Since the sum of the inner angles of the triangle is 180 degrees.

So the triangle can't have 2 or 3 right angles. Thus, a triangle without obtuse angles is either a right triangle with 1 right angle and 2 acute angles; Either an acute triangle with 3 acute angles.

It is an acute triangle or a right triangle.

1. When all three corners are acute angles, there are the following three situations:

When the three sides of the triangle are not equal, the triangle is an ordinary acute triangle;

When the triangle has equal sides, the triangle is an isosceles acute triangle;

When a triangle has three equal sides, the triangle is equilateral;

2. When there is an angle that is a right angle, there are two cases:

When there are two sides equal, the triangle is an isosceles right triangle;

When the three sides are not equal, the triangle is a normal right triangle.

It may be an acute triangle or a right triangle. Reason:

Without obtuse angles, no angle exceeds 90 degrees, and such angles are acute and right-angled.

When all 3 corners of the triangle are acute, the triangle is an acute triangle.

When one of the corners of the triangle is a right angle, then the triangle is a right triangle.

A right triangle or a 60-degree equilateral triangle (all three angles are 60 degrees) or an acute triangle.

Because the sum of the inner angles of the triangle must be 180 degrees, if one of the corners is obtuse, then the sum of the other two angles must be less than 90 degrees; If one of the angles is not obtuse, then the sum of the remaining two angles is greater than or equal to 90 degrees. If there are no obtuse angles, they are the three triangles mentioned above.