There are two questions that have been mixed up here.
There are three "main" types of angle: Acute, Obtuse and Reflex. Acute angles are from 1 to 89 degrees, Obtuse angles from 91 to 179 and Reflex angles anything over 181 degrees. An angle of 90 degrees is a right angle, and an angle of 180 degrees is just a line.
There are three types of triangle: Equilateral, Isosceles and Scalene. Equilateral triangles have all three sides the same length (and the angles are all 60 degrees), isosceles triangles have two equal-length sides of length and two equal angles, and scalene triangles have all three sides different lengths, and all three angles are different.
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isocles, equilateral, obtuse, acute, scalene, right
Triangles without right angles are:- Scalene triangles Obtuse triangles Isosceles triangles Equilateral triangles
A scalene triangle is a triangle in which all three sides have different lengths. The difference between a scalene right triangle and a scalene obtuse triangle is that in the first one, we can find the measure length of the third side when we know the lengths of the two other sides, and in the second one we cannot.
No, they are not always obtuse, because a scalene triangle can also sometimes be an obtuse triangle (meaning that one interior angle is obtuse), making one exterior angle acute. Scalene triangles also can be a right triangles (meaning that one interior angle is a right angle), which would make an exterior angle a right angle. Then also they can be acute triangles, in this case all 3 exterior angles are obtuse.
They are: equilateral, isosceles, obtuse, scalene and right angle triangles