To classify a triangle based on its angles, we can use the following definitions:
- Acute triangle: All angles are less than 90°.
- Right triangle: One angle is exactly 90°.
- Obtuse triangle: One angle is greater than 90°.
In this case, the angles of the triangle are 46°, 51°, and 83°.
Since all angles are less than 90°, the triangle is classified as an acute triangle.
Therefore, the correct response is acute triangle.