A triangle has at most several obtuse angles.

A triangle can have at most one obtuse angle.

An obtuse angle is an angle greater than 90 degrees but less than 180 degrees. In a triangle, the sum of three internal angles is equal to 180 degrees. If a triangle has two or more obtuse angles, their sum will exceed 180 degrees, which violates the basic properties of a triangle. So a triangle can only have an obtuse angle at most.

The characteristics of obtuse angles in geometry are as follows:

1, the obtuse angle consists of two rays.

2. An obtuse angle is a bad angle, that is, an angle greater than 90 degrees but less than 180 degrees.

3. The obtuse angle must be the second quadrant angle, but the second quadrant angle is not necessarily the obtuse angle.

4. Among the trigonometric function values of obtuse angles, the sine value (sin) is positive, while the cosine value (cos), tangent value (tan) and cotangent value (cot) are negative.

5. An obtuse angle has no diagonal (except right angle), that is, an obtuse angle cannot be divided into two equal small angles by a line segment.

6. In a triangle, if there is an obtuse angle, then the triangle must be an isosceles triangle.

7. The obtuse angle can't be measured, which means we can't get the exact degree of the obtuse angle by measurement.

8. In Euclidean geometry, an obtuse angle can be expressed as the difference between two acute angles or as the difference between two angles, one of which is an obtuse angle.

9. When two lines intersect at an obtuse angle, an open three-dimensional space will be formed. For example, in squares, stadiums and other open spaces, you can often see this obtuse structure.

10. In three-dimensional space, an obtuse angle can also indicate the direction of an object or surface. For example, in photography, photographers often use the angle of "down shot" or "up shot" to express the shape and three-dimensional sense of an object. At this time, the angle formed by the camera lens and the surface of the object is obtuse.

In space geometry, obtuse angle can also represent the angle formed by one face of a tetrahedron and another face, or the angle formed by one plane and another plane.