1, with a right triangle: a right triangle is a special measuring tool, and its two right angles are perpendicular to each other. When we use a right triangle to measure an angle, if the angle coincides with the right angle of the right triangle, then the angle is a right angle.

2. Use the characteristics of known right angles: If an angle is adjacent to a known right angle and their sides are on a straight line, then the angle is a right angle.

3. Use a flashlight or sunlight: use a flashlight or sunlight to illuminate an object from one side and then observe whether there is a shadow on the other side. If the shadow forms a straight line, then this angle is a right angle.

4. Use a pencil and ruler: first determine a point with a ruler, and then put the pencil on this point so that the pencil and ruler are vertical. If the angle between the pencil and the ruler is 90 degrees, then this angle is a right angle.

5. Use diagonal lines: If the diagonal lines of a square or rectangle are perpendicular to each other, then the included angle between the two diagonal lines is a right angle.

6. Use the stability of the triangle: nail three pieces of wood into a triangle. If all three angles of a triangle are right angles, then the triangle is stable.

Matters needing attention when judging right angles:

1. Determine the vertex of an angle: When judging whether an angle is a right angle, you must first determine the vertex of the angle. An angle has only one vertex, and the vertex is the starting point of the angle. If two vertices appear in the process of judgment, it will lead to misjudgment of angle.

2. Determine the size of the angle: the size of the right angle is fixed, which is 90 degrees. When judging whether an angle is a right angle, it is necessary to determine whether the angle is 90 degrees. If the size of an angle is not within 90 degrees, then the angle is not a right angle.

3. Pay attention to the side length of the angle: a right angle consists of two sides and forms a vertex at the point where the two sides intersect. If it is found that the side length of an angle is not parallel and does not intersect with the vertex in the judgment process, then the angle is not a right angle. In addition, you need to pay attention to whether the length of both sides is equal. If the two sides are not equal in length, then this angle is not a right angle.